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In [[probability]] and [[statistics]], the '''Tweedie distributions''' are a family of [[probability distribution]]s which include the purely continuous [[normal distribution|normal]] and [[gamma distribution|gamma]] distributions, the purely discrete scaled [[Poisson distribution]], and the class of mixed compound Poisson–gamma distributions which have positive mass at zero, but are otherwise continuous.<ref name="t84">{{cite conference | |||
|last=Tweedie |first=M.C.K. | |||
|year=1984 | |||
|title=An index which distinguishes between some important exponential families | |||
|booktitle=Statistics: Applications and New Directions | |||
|conference=Proceedings of the Indian Statistical Institute Golden Jubilee International Conference | |||
|editor1-first=J.K. |editor1-last=Ghosh | |||
|editor2-first=J |editor2-last=Roy | |||
|pages=579–604 | |||
|publisher=Indian Statistical Institute |location=Calcutta | |||
|mr=786162 | |||
}}</ref> For any [[random variable]] ''Y'' that obeys a Tweedie distribution, the [[variance]] var(''Y'') relates to the [[mean]] E(''Y'') by the power law, | |||
: <math>\text{var}\,(Y) = a[\text{E}\,(Y)]^p ,</math> | |||
where ''a'' and ''p'' are positive constants. | |||
The Tweedie distributions were named by Bent Jørgensen<ref>{{cite journal|last=Jørgensen, B|title=Exponential dispersion models|journal=[[Journal of the Royal Statistical Society]], Series B|year=1987|volume=49|issue=2|pages=127–162|jstor=2345415}}</ref> after [[Maurice Tweedie]], a statistician and medical physicist at the [[University of Liverpool]], UK, who presented the first thorough study of these distributions in 1984.<ref name="t84"/><ref>{{cite journal | |||
|last=Smith |first=C.A.B. |authorlink=Cedric Smith (statistician) | |||
|year=1997 | |||
|title=Obituary: Maurice Charles Kenneth Tweedie, 1919-96 | |||
|journal=[[Journal of the Royal Statistical Society]]: Series A | |||
(Statistics in Society) | |||
|volume=160 |issue=1 |pages=151–154 |doi=10.1111/1467-985X.00052 | |||
}}</ref> | |||
==Examples== | |||
The Tweedie distributions include a number of familiar distributions as well as some unusual ones, each being specified by the [[Domain (mathematical analysis)|domain]] of the index parameter. We have the | |||
*[[normal distribution]], ''p=0'', | |||
*[[Poisson distribution]], ''p=1'', | |||
*compound Poisson–gamma distribution, ''1<p<2'', | |||
*[[gamma distribution]], ''p=2'', | |||
*positive [[stable distribution]]s, ''2<p<3'', | |||
*[[inverse Gaussian distribution]], ''p=3'', | |||
*positive stable distributions, ''p>3'', and | |||
*extreme stable distributions, ''p''={{math|<VAR>∞</VAR>}}. | |||
For 0<''p''<1 no Tweedie model exists. | |||
==Definitions== | |||
Tweedie distributions are a special case of [[exponential dispersion model]]s, a class of models used to describe error distributions for the [[generalized linear model]].<ref | |||
name="Jørgensen-1997">{{cite book | |||
| author = Jørgensen, Bent | |||
| year = 1997 | |||
| title = The theory of dispersion models | |||
| publisher = Chapman & Hall | |||
| isbn = 978-0412997112 | |||
}}</ref> The term exponential dispersion model refers to the [[Exponential family|exponential form]] that these models take, evident from the canonical equation used to describe the distribution ''P<sub>λ,θ</sub>'' of the random variable ''Z'' on the [[Measure (mathematics)|measurable sets]] ''A'', | |||
: <math>P_{\lambda,\theta}(Z\in A)=\int_{A} \exp[\theta \cdot z-\lambda\kappa(\theta)]\cdot \nu_\lambda\, (dz)</math>, | |||
with the interrelated [[Measure (mathematics)|measures]] ''ν<sub>λ</sub>''. ''θ'' is the [[Exponential family|canonical parameter]]; the cumulant function is | |||
: <math>\kappa(\theta)=\lambda^{-1}\log\int e^{\theta z}\cdot \nu_\lambda\, (dz)</math>; | |||
''λ'' is the index parameter; and ''z'' the canonical statistic. This equation represents a family of exponential dispersion models ''ED<sup>*</sup>(θ,λ)'' that are completely determined by the parameters ''θ'' and ''λ'' and the cumulant function. | |||
===Additive exponential dispersion models=== | |||
The models just described are additive models with the property that the distribution of the sum of independent random variables, | |||
: <math>Z_+ = Z_1 +\ldots+ Z_n</math>, | |||
for which ''Z<sub>i</sub>~ED<sup>*</sup>(θ,λ<sub>i</sub>)'' with fixed ''θ'' and various ''λ'' are members of the family of distributions with the same ''θ'', | |||
: <math>Z_+ \sim ED^*(\theta,\lambda_1+\ldots+\lambda_n)</math>. | |||
===Reproductive exponential dispersion models=== | |||
A second class of exponential dispersion models exists designated by the random variable | |||
: <math>Y=Z/\lambda \sim ED(\mu,\sigma^2)</math>, | |||
where ''σ<sup>2</sup>=1/λ'', known as reproductive exponential dispersion models. They have the property that for ''n'' independent random variables ''Y<sub>i</sub>~ED(μ,σ<sup>2</sup>/w<sub>i</sub>)'', with weighting factors ''w<sub>i</sub>'' and | |||
: <math>w= \sum_{i=1}^n w_i</math>, | |||
a weighted average of the variables gives, | |||
: <math>w^{-1}\sum_{i=1}^n w_iY_i \sim ED(\mu,\sigma^2/w)</math>. | |||
For reproductive models the weighted average of independent random variables with fixed ''μ'' and ''σ<sup>2</sup>'' and various values for ''w<sub>i</sub>'' is a member of the family of distributions with same ''μ'' and ''σ<sup>2</sup>''. | |||
The Tweedie exponential dispersion models are both additive and reproductive; we thus have the ''duality transformation'' | |||
: <math>Y \mapsto Z=Y/\sigma^2</math>. | |||
===Scale invariance=== | |||
A third property of the Tweedie models is that they are [[Scale invariance|scale invariant]]: For a reproductive exponential dispersion model ''ED(μ,σ<sup>2</sup>)'' and any positive constant ''c'' we have the property of closure under scale transformation, | |||
: <math>c ED(\mu,\sigma^2)=ED(c\mu,c^{2-p}\sigma^2)</math>, | |||
where the index parameter ''p'' is a real-valued unitless constant. With this transformation the new variable ''Y’=cY'' belongs to the family of distributions with fixed ''μ'' and ''σ<sup>2</sup>'' but different values of ''c''. | |||
===The Tweedie power variance function=== | |||
To define the variance function for exponential dispersion models we make use of the mean value mapping, the relationship between the canonical parameter ''θ'' and the mean ''μ''. It is define by the function | |||
: <math>\tau(\theta)=\kappa^\prime(\theta)=\mu</math>. | |||
The [[Natural exponential family|variance function]] ''V(μ)'' is constructed from the mean value mapping, | |||
: <math>V(\mu)=\tau^\prime[\tau^{-1}(\mu)]</math>. | |||
Here the minus exponent in ''τ<sup> -1</sup>(μ)'' denotes an inverse function rather than a reciprocal. The mean and variance of an additive random variable is then E''(Z)=λμ'' and var''(Z)=λV(μ). | |||
Scale invariance implies that the variance function obeys the relationship | |||
''V(μ)=μ<sup> p</sup>.<ref | |||
name="Jørgensen-1997">{{cite book | |||
| author = Jørgensen, Bent | |||
| year = 1997 | |||
| title = The theory of dispersion models | |||
| publisher = [Chapman & Hall] | |||
| isbn = 978-0412997112 | |||
}}</ref> | |||
===The Tweedie cumulant generating functions=== | |||
The properties of exponential dispersion models give us two [[differential equation]]s.<ref | |||
name="Jørgensen-1997">{{cite book | |||
| author = Jørgensen, Bent | |||
| year = 1997 | |||
| title = The theory of dispersion models | |||
| publisher = [Chapman & Hall] | |||
| isbn = 978-0412997112 | |||
}}</ref> The first relates the mean value mapping and the variance function to each other, | |||
: <math>\frac{\partial \tau^{-1}(\mu)}{\partial \mu}= \frac{1}{V(\mu)}</math>. | |||
The second shows how the mean value mapping is related to the [[cumulant|cumulant function]], | |||
: <math>\frac{\partial \kappa(\theta)}{\partial \theta}=\tau(\theta)</math>. | |||
These equations can be solved to obtain the cumulant function for different cases of the Tweedie models. A cumulant generating function (CGF) may then be obtained from the cumulant function. The additive CGF is generally specified by the equation | |||
: <math>K^*(s)=\log[\text{E}(e^{sZ})]=\lambda[\kappa(\theta+s)-\kappa(\theta)]</math>, | |||
and the reproductive CGF by | |||
: <math>K(s)=\log[\text{E}(e^{sY})]=\lambda[\kappa(\theta+s/\lambda)-\kappa(\theta)]</math>, | |||
where ''s'' is the generating function variable. | |||
The cumulant functions for specific values of the index parameter ''p'' are<ref | |||
name="Jørgensen-1997">{{cite book | |||
| author = Jørgensen, Bent | |||
| year = 1997 | |||
| title = The theory of dispersion models | |||
| publisher = [Chapman & Hall] | |||
| isbn = 978-0412997112 | |||
}}</ref> | |||
: <math>\kappa_p(\theta) = \begin{cases} \dfrac{\alpha-1}{\alpha} \left(\dfrac{\theta}{\alpha-1}\right)^\alpha | |||
& \quad p \ne 1,2 \\ -\log(-\theta) & \quad p = 2 \\ e^\theta & \quad p = 1 \end{cases} | |||
</math>, | |||
where ''α'' is the Tweedie exponent | |||
: <math>\alpha=\dfrac{p-2}{p-1}</math>. | |||
For the additive Tweedie models the CGFs take the form, | |||
: <math>K^*_p(s;\theta,\lambda) = \begin{cases} \lambda\kappa_p(\theta)[(1+s/\theta)^\alpha-1] | |||
& \quad p \ne 1,2 \\ -\lambda \log(1+s/\theta) & \quad p = 2 \\ \lambda e^\theta (e^s -1) & \quad p = 1 \end{cases} | |||
</math>, | |||
and for the reproductive models, | |||
: <math>K_p(s;\theta,\lambda) = \begin{cases} \lambda\kappa_p(\theta)\left \{ [1+s/(\theta \lambda)]^\alpha-1 \right \} | |||
& \quad p \ne 1,2 \\ -\lambda \log[1+s/(\theta \lambda)] & \quad p = 2 \\ \lambda e^\theta (e^{s/\lambda} -1) & \quad p = 1 \end{cases} | |||
</math>. | |||
The additive and reproductive Tweedie models are conventionally denoted by the symbols ''Tw<sup>*</sup><sub>p</sub>(θ,λ)'' and ''Tw<sub>p</sub>(θ,σ<sup>2</sup>)'', respectively. | |||
The first and second derivatives of the CGFs, with ''s=0'', yields the mean and variance, respectively. One can thus confirm that for the additive models the variance relates to the mean by the power law, | |||
: <math>\mathrm{var} (Z)\propto \mathrm{E}(Z)^p</math>. | |||
==The Tweedie convergence theorem== | |||
The Tweedie exponential dispersion models are fundamental in statistical theory consequent to their roles as foci of [[convergence in distribution|convergence]] for a wide range of statistical processes. Jørgensen ''et al'' proved a theorem that specifies the asymptotic behaviour of variance functions known as the Tweedie convergence theorem".<ref>{{cite journal|last=Jørgensen, B|coauthors=Martinez, JR & Tsao, M|title=Asymptotic behaviour of the variance function|journal=Scandinavian Journal of Statistics|year=1994|volume=21|pages=223–243}}</ref> This theorem, in technical terms, is stated thus:<ref | |||
name="Jørgensen-1997">{{cite book | |||
| author = Jørgensen, Bent | |||
| year = 1997 | |||
| title = The theory of dispersion models | |||
| publisher = [Chapman & Hall] | |||
| isbn = 978-0412997112 | |||
}}</ref> The unit variance function is regular of order ''p'' at zero (or infinity) provided that ''V(μ)~c<sub>0</sub>μ<sup>p</sup>'' for ''μ'' as it approaches zero (or infinity) for all real values of ''p'' and ''c<sub>0</sub> >0''. Then for a unit variance function regular of order ''p'' at either zero or infinity and for | |||
: <math>p \notin (0,1)</math> , | |||
for any <math>\mu>0</math>, and <math> \sigma^2>0</math> we have | |||
: <math>c^{-1} ED(c\mu,\sigma^2c^{2-p}) \rightarrow Tw_p(\mu,c_0 \sigma^2)</math> | |||
as <math>c \downarrow 0</math> or <math>c \rightarrow \infty</math>, respectively, where the convergence is through values of ''c'' such that ''cμ'' is in the domain of ''θ'' and ''c<sup>p-2</sup>/σ<sup>2</sup>'' is in the domain of ''λ''. The model must be infinitely divisible as ''c<sup>2-p</sup>'' approaches infinity.<ref | |||
name="Jørgensen-1997">{{cite book | |||
| author = Jørgensen, Bent | |||
| year = 1997 | |||
| title = The theory of dispersion models | |||
| publisher = [Chapman & Hall] | |||
| isbn = 978-0412997112 | |||
}}</ref> | |||
In nontechnical terms this theorem implies that any exponential dispersion model that asymptotically manifests a variance-to-mean power law is required to have a variance function that comes within the [[Attractor|domain of attraction]] of a Tweedie model. Almost all distribution functions with finite cumulant generating functions qualify as exponential dispersion models and most exponential dispersion models manifest variance functions of this form. Hence many probability distributions have variance functions that express this asymptotic behavior, and the Tweedie distributions become foci of convergence for a wide range of data types.<ref name=Kendal2011b>{{cite doi|10.1103/PhysRevE.84.066120}}</ref> | |||
==The Tweedie models and Taylor’s power law== | |||
[[Taylor's law]] is an empirical law in [[ecology]] that relates the variance of the number of individuals of a species per unit area of habitat to the corresponding mean by a [[power-law]] relationship.<ref name=Taylor1961>Taylor LR (1961) Aggregation, variance and the mean. ''Nature'' 189, 732–735</ref> For the population count ''Y'' with mean ''µ'' and variance var(''Y''), Taylor’s law is written, | |||
: <math>\text{var}\,(Y) = a\mu^p</math>, | |||
where ''a'' and ''p'' are both positive constants. Since L. R. Taylor described this law in 1961 there have been many different explanations offered to explain it, ranging from animal behavior,<ref name="Taylor1961" /> a [[random walk]] model,<ref name=Hanski1980>Hanski I (1980) Spatial patterns and movements in coprophagous beetles. ''Oikos'' 34, 293-310</ref> a [[birth-death process|stochastic birth, death, immigration and emigration model]],<ref name=Anderson1961>Anderson RD, Crawley GM & Hassell M (1982) Variability in the abundance of animal and plant species. ''Nature'' 296, 245–248</ref> to a consequence of equilibrium and non-equilibrium [[statistical mechanics]].<ref name=Fronczak2010>Fronczak A & Fronczak P (2010) Origins of Taylor’s power law for fluctuation scaling in complex systems. ''Phys Rev E'' 81, 066112</ref> No consensus exists as to an explanation for this model. | |||
Since Taylor’s law is mathematically identical to the variance-to-mean power law that characterizes the Tweedie models, it seemed reasonable to use these models and the Tweedie convergence theorem to explain the observed clustering of animals and plants associated with Taylor’s law.<ref name=Kendal2002>Kendal WS (2002) Spatial aggregation of the Colorado potato beetle described by an exponential dispersion model. ''Ecological Modelling'' 151, 261–269</ref><ref name=Kendal2004>Kendal WS (2004) Taylor’s ecological power law as a consequence of scale invariant exponential dispersion models. ''Ecol Complex'' 1, 193–209</ref> The majority of the observed values for the power-law exponent ''p'' have fallen in the interval (1,2) and so the Tweedie compound Poisson–gamma distribution would seem applicable. Comparison of the [[empirical distribution function]] to the theoretical compound Poisson–gamma distribution has provided a means to verify consistency of this hypothesis.<ref name="Kendal2002" /> | |||
Whereas conventional models for Taylor’s law have tended to involve ''[[ad hoc]]'' animal behavioral or [[population dynamics|population dynamic]] assumptions, the Tweedie convergence theorem would imply that Taylor’s law results from a general mathematical convergence effect much as how the [[central limit theorem]] governs the convergence behavior of certain types of random data. Indeed, any mathematical model, approximation or simulation that is designed to yield Taylor’s law (on the basis of this theorem) is required to converge to the form of the Tweedie models.<ref name=Kendal2011b>Kendal WS & Jørgensen BR (2011) Tweedie convergence: a mathematical basis for Taylor's power law, ''1/f'' noise and multifractality. ''Phys. Rev E'' 84, 066120</ref> | |||
==The double power law== | |||
The [[eponym]] Taylor's power law has been applied to a wide range of data that manifests a variance-to-mean power function. However, subtle mathematical differences exist between the [[transformation (function)|transformational]] properties of some of these data. A double power law, which includes Taylor’s original law, has been proposed to describe these differences.<ref name=Jørgensen2011>Jørgensen B, Martinez JR & Demetrio CGB (2011) Self-similarity and Lamperti convergence for families of stochastic processes. ''Lith Math J'' 51, 342–362</ref> For a population count drawn from an area of size ''t'' with mean abundance per unit area ''µ'', and where | |||
: <math>\text{E}\,[Y(\mu;t)] = t\mu\,\!</math>, | |||
we have for the double power law: | |||
: <math>\text{var}\,[Y(\mu;t)] = a\mu^pt^{2-d}\,\!</math>. | |||
The constant ''d''{{math|<VAR>∈</VAR>}} [0,1] has been identified as a [[Fractal dimension#Role of scaling|fractal exponent]]. The factor ''aµ''<sup>'' p''</sup> represents the original Taylor’s law, a function of the mean abundance per unit area; the last term ''t''<sup>2-''d''</sup> describes how the power law scales with the enumerative bin size. This last term implies a statistically [[self-similarity|self-similar]] scaling of the spatial distribution of items of interest as the size of the bin changes. It is this second portion of the double power law that underlies the variance-to-mean power law reported in systems like regional blood flow heterogeneity,<ref name=Kendal2001>Kendal WS (2001) A stochastic model for the self-similar heterogeneity of regional organ blood flow. ''Proc Natl Acad Sci U S A'' 98, 837-841</ref> the genomic distribution of SNPs<ref name=Kendal2003>Kendal WS (2003) An exponential dispersion model for the distribution of human single nucleotide polymorphisms" ''Mol Biol Evol'' 20 579-590</ref> and genes,<ref name=KendalGenes>{{cite journal|last=Kendal|first=WS|title=A scale invariant clustering of genes on human chromosome 7|journal=BMC Evol Biol|year=2004|volume=4|pages=3|doi=10.1186/1471-2148-4-3}}</ref> and [[number theory|number theoretic]] examples.<ref name="Kendal2011b" /><ref name=Kendal2011a>Kendal WS & Jørgensen B (2011) Taylor's power law and fluctuation scaling explained by a central-limit-like convergence. ''Phys. Rev. E'' 83,066115</ref> | |||
==Tweedie convergence and 1/''f'' noise== | |||
[[Pink noise]], or 1/''f'' noise, refers to a pattern of noise characterized by a power-law relationship between its intensities ''S(f)'' at different frequencies ''f'', | |||
: <math>S(f)\propto 1/f^{ \gamma}</math>, | |||
where the dimensionless exponent ''γ''{{math|<VAR>∈</VAR>}} [0,1]. It is found within a diverse number of natural processes.<ref name=Dutta1981>Dutta P & Horn PM (1981) Low frequency fluctuations in solids: ''1/f'' noise. ''Rev Mod Phys'' 53,497-516</ref> Many different explanations for ''1/f'' noise exist, a widely held hypothesis is based on [[Self-organized criticality]] where dynamical systems close to a [[Critical point (thermodynamics)|critical point]] are thought to manifest [[scale-invariance|scale-invariant]] spatial and/or temporal behavior. | |||
In this subsection a mathematical connection between ''1/f'' noise and the Tweedie variance-to-mean power law will be described. To begin, we first need to introduce [[self-similar process]]es: For the sequence of numbers | |||
: <math>Y=(Y_i :i=0,1,2,...,N)</math> | |||
with mean | |||
: <math>\hat{\mu}=\text{E}(Y_i)</math>, | |||
deviations | |||
: <math>y_i = Y_i - \hat{\mu} </math>, | |||
variance | |||
: <math>\hat{\sigma}^2=\text{E}(y_i^2)</math>, | |||
and autocorrelation function | |||
: <math>r(k)=\text{E}(y_i,y_{i+k})/\text{E}(y_i^2)</math> | |||
with lag ''k'', if the [[autocorrelation]] of this sequence has the long range behavior | |||
: <math>r(k)\sim k^{-d} L(k) </math> | |||
as ''k''{{math|<VAR>→∞</VAR>}} and where ''L(k)'' is a slowly varying function at large values of ''k'', this sequence is called a self-similar process.<ref name=Leland1994>Leland WE, Taqqu MS, Willinger W & Wilson DV (1994) On the self-similar nature of ethernet traffic. ''IEE/ACM Trans Networking'' 2, 1-15</ref> | |||
The '''method of expanding bins''' can be used to analyze self-similar processes. Consider a set of equal-sized non-overlapping bins that divides the original sequence of ''N'' elements into groups of ''m'' equal-sized segments (''N/m'' is integer) so that new reproductive sequences, based on the mean values, can be defined: | |||
: <math>Y_i^{(m)}=(Y_{im-m+1}+...+Y_{im})/m</math>. | |||
The variance determined from this sequence will scale as the bin size changes such that | |||
: <math>\text{var}[Y^{(m)}]=\hat{\sigma}^2 m^{-d}</math> | |||
if and only if the autocorrelation has the limiting form<ref name=Tsybakov1997>Tsybakov B & Georganas ND (1997) On self-similar traffic in ATM queues: definitions, overflow probability bound, and cell delay distribution. ''IEEE/ACM Trans Networking'' 5, 397–409</ref> | |||
: <math>\lim_{k \to \infty}r(k)/k^{-d} = (2-d)(1-d)/2</math>. | |||
One can also construct a set of corresponding additive sequences | |||
: <math>Z_i^{(m)} = mY_i^{(m)}</math>, | |||
based on the expanding bins, | |||
: <math>Z_i^{(m)}=(Y_{im-m+1}+...+Y_{im})</math>. | |||
Provided the autocorrelation function exhibits the same behavior, the additive sequences will obey the relationship | |||
: <math>\text{var}[Z_i^{(m)}]=m^2 \text{var}[Y^{(m)}]=(\hat{\sigma}^2 /\hat{\mu}^{2-d})\text{E}[Z_i^{(m)}]^{2-d}</math> | |||
Since <math>\hat{\mu}</math> and <math>\hat{\sigma}^2</math> are constants this relationship constitutes a variance-to-mean power law, with ''p''=2-''d''.<ref name="Kendal2011b" /><ref name=Kendal2007>Kendal WS (2007) Scale invariant correlations between genes and SNPs on Human chromosome 1 reveal potential evolutionary mechanisms. ''J Theor Biol'' 245, 329-340</ref> | |||
The [[Logical biconditional|biconditional]] relationship above between the variance-to-mean power law and power law autocorrelation function, and the [[Wiener–Khinchin theorem]]<ref name=McQuarrie1976>McQuarrie DA (1976) ''Statistical mechanics'' [Harper & Row]</ref> imply that any sequence that exhibits a variance-to-mean power law by the method of expanding bins will also manifest ''1/f'' noise, and vice versa. Moreover, the Tweedie convergence theorem, by virtue of its central limit-like effect of generating distributions that manifest variance-to-mean power functions, will also generate processes that manifest ''1/f'' noise.<ref name="Kendal2011b" /> The Tweedie convergence theorem thus allows provides an alternative explanation for the origin of ''1/f'' noise, based its central limit-like effect. | |||
Much as the [[central limit theorem]] requires certain kinds of random processes to have as a focus of their convergence the [[normal distribution|Gaussian distribution]] and thus express [[white noise]], the Tweedie convergence theorem requires certain non-Gaussian processes to have as a focus of convergence the Tweedie distributions that express ''1/f'' noise.<ref name="Kendal2011b" /> | |||
==The Tweedie models and multifractality== | |||
From the properties of self-similar processes, the power-law exponent ''p''=2-''d'' is related to the [[Hurst exponent]] ''H'' and the [[fractal dimension]] ''D'' by<ref name="Tsybakov1997" /> | |||
: <math>D = 2-H = 2 - p/2 </math>. | |||
A one-dimensional data sequence of self-similar data may demonstrate a variance-to-mean power law with local variations in the value of ''p'' and hence in the value of ''D''. When fractal structures manifest local variations in fractal dimension, they are said to be [[multifractal system|multifractals]]. Examples of data sequences that exhibit local variations in ''p'' like this include the eigenvalue deviations of the [[Random matrix|Gaussian Orthogonal and Unitary Ensembles]].<ref name="Kendal2011b" /> The Tweedie compound Poisson–gamma distribution has served to model multifractality based on local variations in the Tweedie exponent ''α''. Consequently, in conjunction with the variation of ''α'', the Tweedie convergence theorem can be viewed as having a role in the genesis of such multifractals. | |||
The variation of ''α'' has been found to obey the asymmetric [[Laplace distribution|Laplace distribution]] in certain cases. <ref name=Kendal2014>Kendal WS (2014) Multifractality attributed to dual central limit-lie convergence effects. ''Physica A'' 401, 22-33</ref> This distribution has been shown to be a member of the family of geometric Tweedie models <ref name=Jørgensen2011> Jørgensen B, Kokonendji CC (2011) Dispersion models for geometric sums. ''Braz J Probab Stat'' 25, 263-293</ref>, that manifest as limiting distributions in a convergence theorem for geometric dispersion models. | |||
==Applications== | |||
===Regional organ blood flow=== | |||
Regional organ blood flow has been traditionally assessed by the injection of [[Isotopic labeling|radiolabelled]] [[polyethylene microspheres]] into the arterial circulation of animals, of a size that they become entrapped within the [[microcirculation]] of organs. The organ to be assessed is then divided into equal-sized cubes and the amount of radiolabel within each cube is evaluated by [[liquid scintillation counting]] and recorded. The amount of radioactivity within each cube is taken to reflect the blood flow through that sample at the time of injection. It is possible to evaluate adjacent cubes from an organ in order to additively determine the blood flow through larger regions. Through the work of '''J B Bassingthwaighte''' and others an empirical power law has been derived between the relative dispersion of blood flow of tissue samples (''RD''=standard deviation/ mean)of mass ''m'' relative to reference sized samples:<ref name=Bassingthwaighte1989>Bassingthwaighte JB (1989) Fractal nature of regional myocardial blood flow heterogeneity. ''Circ Res'' 65, 578-590</ref> | |||
: <math>RD(m)=RD(m_{ref})\left (\frac{m}{m_{ref}}\right )^{1-D_s}</math> | |||
This power law exponent ''D<sub>s</sub>'' has been called a fractal dimension. '''Bassingthwaighte’s power law''' can be shown to directly relate to the variance-to-mean power law. Regional organ blood flow can thus be modelled by the Tweedie compound Poisson–gamma distribution.<ref name="Kendal2001" /> In this model tissue sample could be considered to contain a random (Poisson) distributed number of entrapment sites, each with [[gamma distribution|gamma distributed]] blood flow. Blood flow at this microcirculatory level has been observed to obey a gamma distribution,<ref>Honig CR, Feldstein ML, Frierson JL. 1977. Capillary lengths, anastomoses, and estimated capillary transit times in skeletal muscle. Am J Physiol Heart Circul Physiol 233: H122--H129.</ref> thus providing support for this hypothesis. | |||
===Cancer metastasis=== | |||
The "experimental cancer [[metastasis]] assay"<ref name=Fidler1977>{{cite journal|last=Fidler|first=IJ|coauthors=Kripke, M|title=Metastasis results from preexisting variant cells within a malignant tumor|journal=Science|year=1977|volume=197|pages=893–895|bibcode = 1977Sci...197..893F |doi = 10.1126/science.887927 }}</ref> has some resemblance to the above method to measure regional blood flow. Groups of [[syngeneic]] and age matched mice are given intravenous injections of equal-sized aliquots of suspensions of cloned cancer cells and then after a set period of time their lungs are removed and the number of cancer metastases enumerated within each pair of lungs. If other groups of mice are injected with different cancer cell [[Clone (cell biology)|clones]] then the number of metastases per group will differ in accordance with the metastatic potentials of the clones. It has been long recognized that there can be considerable intraclonal variation in the numbers of metastases per mouse despite the best attempts to keep the experimental conditions within each clonal group uniform.<ref name=Fidler1977>Fidler IJ & Kripke M. 1977. Metastasis results from pre-existing variant cells within a malignant tumor" ''Science'' 197: 893--895.</ref> This variation is larger than would be expected on the basis of a [[Poisson distribution]] of numbers of metastases per mouse in each clone and when the variance of the number of metastases per mouse was plotted against the corresponding mean a power law was found.<ref name=Kendal1987>Kendal WS & Frost P (1987) Experimental metastasis: a novel application of the variance-to-mean power function. ''J Natl Cancer Inst'' 79, 1113-1115</ref> | |||
The variance-to-mean power law for metastases was found to also hold for '''spontaneous murine metastases'''<ref>Kendal WS. 1999. Clustering of murine lung metastases reflects fractal nonuniformity in regional lung blood flow. Invasion Metastasis 18: 285--296.</ref> and for cases series of human metastases.<ref>Kendal WS, Lagerwaard, FJ & Agboola O. 2000. Characterization of the frequency distribution for human hematogenous metastases: evidence for clustering and a power variance function. Clin Exp Metastasis 18: 219--229.</ref> | |||
Since hematogenous metastasis occurs in direct relationship to regional blood flow<ref>Weiss L, Bronk J, Pickren JW & Lane WW. 1981. Metastatic patterns and targe organ arterial blood flow. Invasion Metastasis 1: 126--135.</ref> and videomicroscopic studies indicate that the passage and entrapment of cancer cells within the circulation appears analogous to the microsphere experiments<ref>Chambers AF, Groom AC & MacDonald IC. 2002. Dissemination and growth of cancer cells in metastatic sites. Nature Rev Cancer 2: 563--572.</ref> it seemed plausible to propose that the variation in numbers of hematogenous metastases could reflect heterogeneity in regional organ blood flow.<ref>Kendal WS. 2002. A frequency distribution for the number of hematogenous organ metastases. Invasion Metastasis 1: 126--135.</ref> | |||
The blood flow model was based on the Tweedie compound Poisson–gamma distribution, a distribution governing a continuous random variable. For that reason in the metastasis model it was assumed that blood flow was governed by that distribution and that the number of regional metastases occurred as a [[Poisson process]] for which the intensity was directly proportional to blood flow. This lead to the description of the Poisson negative binomial (PNB) distribution as a [[discrete probability distribution|discrete equivalent]] to the Tweedie compound Poisson–gamma distribution. The [[probability-generating function|probability generating function]] for the PNB distribution is | |||
: <math>G(s)= \exp \left [\lambda \frac {\alpha-1}{\alpha} \left( \frac{\theta} {\alpha-1} \right)^\alpha \left\{ \left(1- \frac{1} {\theta}+ \frac {s} {\theta}\right)^\alpha-1 \right\}\right]</math>. | |||
The relationship between the mean and variance of the PNB distribution is then | |||
: <math>\text{var}\,(Y) = a\text{E}(Y)^b + \text{E}(Y)</math>, | |||
which, in the range of many experimental metastasis assays, would be indistinguishable from the variance-to-mean power law. For sparse data, however, this discrete variance-to-mean relationship would behave more like that of a Poisson distribution where the variance equaled the mean. | |||
===Genomic structure and evolution=== | |||
The local density of [[Single-nucleotide polymorphism|Single Nucleotide Polymorphisms]] (SNPs) within the [[human genome]], as well as that of [[gene]]s, appears to cluster in accord with the variance-to-mean power law and the Tweedie compound Poisson–gamma distribution.<ref name="Kendal2003" /><ref name=KendalGenes /> In the case of SNPs their observed density reflects the assessment techniques, the availability of genomic sequences for analysis, and the [[Nucleotide diversity|nucleotide heterozygosity]].<ref>The international SNP map working group. 2001. A map of human genome variation containing 1.42 million single nucleotide polymorphisms" ''Nature'' 409: 928--933.</ref> The first two factors reflect ascertainment errors inherent to the collection methods, the latter factor reflects an intrinsic property of the genome. | |||
In the [[Coalescent theory|coalescent model]] of population genetics each genetic locus has its own unique history. Within the evolution of a population from some species some genetic loci could presumably be traced back to a relatively [[Most recent common ancestor|recent common ancestor]] whereas other loci might have more ancient [[Genetic genealogy|genealogies]]. More ancient genomic segments would have had more time to accumulate SNPs and to experience [[Genetic recombination|recombination]]. '''R R Hudson''' has proposed a model where recombination could cause variation in the time to [[Most recent common ancestor|most common recent ancestor]] for different genomic segments.<ref>Hudson RR. 1991. Gene genealogies and the coalescent process. Oxford surveys in evolutionary biology 7: 1--44.</ref> A high recombination rate could cause a chromosome to contain a large number of small segments with less correlated genealogies. | |||
Assuming a constant background rate of mutation the number of SNPs per genomic segment would accumulate proportionately to the time to the most recent common ancestor. Current [[population genetics|population genetic theory]] would indicate that these times would be [[gamma distribution|gamma distributed]], on average.<ref>Tavare S, Balding DJ, Griffiths RC & Donnelly P. 1997. Inferring coalescent times from DNA sequence data" ''Genetics'' 145: 505--518.</ref> The Tweedie compound Poisson–gamma distribution would suggest a model whereby the SNP map would consist of multiple small genomic segments with the mean number of SNPs per segment would be gamma distributed as per Hudson’s model. | |||
The distribution of genes within the human genome also demonstrated a variance-to-mean power law, when the method of expanding bins was used to determine the corresponding variances and means.<ref name=KendalGenes /> Similarly the number of genes per enumerative bin was found to obey a Tweedie compound Poisson–gamma distribution. This probability distribution was deemed compatible with two different biological models: the '''microarrangement model''' where the number of genes per unit genomic length was determined by the sum of a random number of smaller genomic segments derived by random breakage and reconstruction of protochormosomes. These smaller segments would be assumed to carry on average a gamma distributed number of genes. | |||
In the alternative '''gene cluster model''', genes would be distributed randomly within the protochromosomes. Over large evolutionary timescales there would occur [[gene duplication|tandem duplication]], [[mutation|mutations, insertions, deletions]] and [[chromosomal rearrangement|rearrangements]] that could affect the genes through a stochastic [[Birth–death process|birth, death and immigration process]] to yield the Tweedie compound Poisson–gamma distribution. | |||
Both these mechanisms would implicate [[Neutral theory of molecular evolution|neutral evolutionary processes]] that would result in regional clustering of genes. | |||
===Random matrix theory=== | |||
The '''[[Random matrix|Gaussian unitary ensemble]]''' (GUE) consists of complex [[Hermitian matrix|Hermitian matrices]] that are invariant under [[unitary transformation]]s whereas the '''[[Random matrix|Gaussian orthogonal ensemble]]''' (GOE) consists of real symmetric matrices invariant under [[orthogonal transformation]]s. The ranked [[Eigenvalues and eigenvectors|eigenvalues]] ''E<sub>n</SUB>'' from these random matrices obey '''[[Wigner semicircle distribution|Wigner’s semicircular distribution]]''': For a ''NxN'' matrix the average density for eigenvalues of size ''E'' will be | |||
: <math>\bar{\rho}(E)= \begin{cases} \sqrt{2N-E^2}/\pi | |||
& \quad \left\vert E \right\vert < \sqrt{2N} \\ 0 & \quad \left\vert E \right\vert > \sqrt{2N} \end{cases} </math> | |||
as ''E''{{math|<VAR>→ ∞ </VAR>}}. Integration of the semicircular rule provides the number of eigenvalues on average less than ''E'', | |||
: <math>\bar{\eta}(E) = \frac{1}{2\pi}\left [E\sqrt{2N-E^2}+2N \arcsin \left( \frac{E}{\sqrt{2N}} \right )+ \pi N \right ] </math>. | |||
The ranked eigenvalues can be '''unfolded''', or renormalized, with the equation | |||
: <math>e_n = \bar{\eta}(E)=\int \limits_{-\infty}^{E_n}dE^\prime \bar{\rho}(E^\prime) </math>. | |||
This removes the trend of the sequence from the fluctuating portion. If we look at the absolute value of the difference between the actual and expected cumulative number of eigenvalues | |||
: <math>\left | \bar{D}_n \right | =\left | n- \bar{\eta}(E_n) \right | </math> | |||
we obtain a sequence of '''eigenvalue fluctuations''' which, using the method of expanding bins, reveals a variance-to-mean power law.<ref name="Kendal2011b" /> | |||
The eigenvalue fluctuations of both the GUE and the GOE manifest this power law with the power law exponents ranging between 1 and 2, and they similarly manifest 1/''f'' noise spectra. These eigenvalue fluctuations also correspond to the Tweedie compound Poisson–gamma distribution and they exhibit multifractality.<ref name="Kendal2011b" /> | |||
===The distribution of [[prime number]]s=== | |||
The '''second [[Chebyshev function]]''' ''ψ''(''x'') is given by, | |||
:<math> \psi(x) = \sum_{\hat{p}^k\le x}\log \hat{p}=\sum_{n \leq x} \Lambda(n) </math> | |||
where the summation extends over all prime powers <math>\hat{p}^k </math> not exceeding ''x'', ''x'' runs over the positive real numbers, and <math>\Lambda(n)</math> is the [[von Mangoldt function]]. The function ''ψ''(''x'') is related to the [[prime-counting function]] ''π''(''x''), and as such provides information with regards to the distribution of prime numbers amongst the real numbers. It is asymptotic to ''x'', a statement equivalent to the [[prime number theorem]] and it can also be shown to be related to the zeros of the [[Riemann zeta function]] located on the critical strip ρ, where the real part of the zeta zero ρ is between 0 and 1. Then ψ expressed for ''x'' greater than one can be written: | |||
:<math>\psi_0(x) = x - \sum_\rho \frac{x^\rho}{\rho} - \ln 2\pi - \frac12 \ln(1-x^{-2})</math> | |||
where | |||
: <math>\psi_0(x) = \lim_{\varepsilon \rightarrow 0}\frac{\psi(x-\varepsilon)+\psi(x+\varepsilon)}2.</math> | |||
The [[Riemann hypothesis]] states that the [[root of a function|nontrivial zeros]] of the [[Riemann zeta function]] all have [[real part]] ½. These zeta function zeros are related to the [[prime number theorem|distribution of prime numbers]]. [[Lowell Schoenfeld|'''Schoenfeld''']]<ref>{{cite journal|last=Schoenfeld|first=J|title=Sharper bounds for the Chebyshev functions θ(x) and ψ(x). II|journal=Math Computation|year=1976|volume=30|issue=134|pages=337–360}}</ref> has shown that if the Riemann hypothesis is true then | |||
: <math> \Delta(x)=\left\vert \psi(x)-x \right\vert < \sqrt{x} \log^{2}(x)/(8 \pi)</math> | |||
for all <math>x>73.2</math>. If we analyze the Chebyshev deviations Δ'' (n)'' on the integers ''n'' using the method of expanding bins and plot the variance versus the mean a variance to mean power law can be demonstrated.<ref>{{cite journal|last=Kendal|first=WS|title=Fluctuation scaling and 1/f noise: shared origins from the Tweedie family of statistical distributions|journal=J Basic Appl Phys|year=2013|volume=2|pages=40–49}}</ref> Moreover, these deviations correspond to the Tweedie compound Poisson-gamma distribution and they exhibit ''1/f'' noise. | |||
===Other applications=== | |||
Applications of Tweedie distributions include: | |||
* actuarial studies<ref>Haberman, S. and Renshaw, A. E. 1996. | |||
Generalized linear models and actuarial science. The Statistician, 45: | |||
407--436.</ref><ref>Renshaw, A. E. 1994. | |||
Modelling the claims process in the presence of covariates. ASTIN | |||
Bulletin 24: 265--286.</ref><ref>Jørgensen, B. and Paes de | |||
Souza, M. C. 1994. Fitting Tweedie's compound Poisson model to insurance | |||
claims | |||
data. Scand. Actuar. J. 1: 69--93.</ref><ref>Haberman, S., | |||
and Renshaw, A. E. 1998. | |||
Actuarial applications of generalized linear models. In Statistics in | |||
Finance, D. J. Hand and S. D. Jacka (eds), Arnold, | |||
London.</ref><ref>Mildenhall, S. J. 1999. A systematic | |||
relationship between minimum bias and generalized linear models. 1999 | |||
Proceedings of the Casualty Actuarial Society 86: | |||
393--487.</ref><ref>Murphy, K. P., Brockman, M. J., and Lee, | |||
P. K. W. (2000). Using generalized linear models to build dynamic | |||
pricing systems. Casualty Actuarial Forum, Winter | |||
2000.</ref><ref>{{cite journal | |||
|last=Smyth |first=G.K. | |||
|last2=Jørgensen |first2=B. | |||
|year=2002 | |||
|title=Fitting Tweedie's compound Poisson model to insurance claims data: dispersion modelling | |||
|journal=ASTIN Bulletin | |||
|volume=32 |pages=143–157 | |||
|url=http://www.casact.org/library/astin/vol32no1/143.pdf | |||
}}</ref> | |||
* assay analysis <ref>Davidian, M. 1990. Estimation of variance | |||
functions in assays with possible unequal | |||
replication and nonnormal data. Biometrika 77: | |||
43--54.</ref><ref>Davidian, M., Carroll, R. J. and Smith, W. | |||
1988. Variance functions and the minimum detectable concentration in | |||
assays. Biometrika 75: 549--556.</ref> | |||
* survival analysis<ref>Aalen, O. O. 1992. Modelling heterogeneity | |||
in survival analysis by the compound Poisson distribution. Ann. Appl. | |||
Probab. 2: 951--972.</ref><ref>Hougaard, P. , Harvald, B. | |||
and Holm, N. V. 1992. Measuring the similarities between the lifetimes | |||
of adult Danish twins born between 1881--1930. Journal of the American Statistical Association | |||
87: 17--24.</ref><ref>Hougaard, P. 1986. Survival models for | |||
heterogeneous populations derived from stable distributions. | |||
Biometrika, 73: 387--396.</ref> | |||
* ecology <ref name=Kendal2002>Kendal WS (2002) Spatial aggregation of the Colorado potato beetle described by an exponential dispersion model. ''Ecol Model'' 151, 261–269</ref> | |||
* analysis of alcohol consumption in British teenagers <ref>Gilchrist, R. and Drinkwater, D. 1999. | |||
Fitting Tweedie models to data with probability of zero responses. | |||
Proceedings of the 14th International | |||
Workshop on Statistical Modelling, Graz, pp. 207--214.</ref> | |||
* medical applications <ref name="smyth1996">Smyth, G. K. 1996. | |||
Regression analysis of quantity data with exact zeros. | |||
Proceedings of the Second Australia--Japan Workshop on Stochastic Models | |||
in Engineering, Technology and Management. Technology Management | |||
Centre, University of Queensland, 572--580.</ref> | |||
* meteorology and climatology <ref name="smyth1996"/><ref>Hasan, M.M.; Dunn, P.K. (2010) "Two | |||
Tweedie distributions that are near-optimal for modelling monthly | |||
rainfall in Australia", ''International Journal of Climatology'', | |||
{{doi|10.1002/joc.2162}}</ref> | |||
* fisheries <ref>Candy, S. G. 2004. Modelling catch and effort | |||
data using generalized linear models, | |||
the Tweedie distribution, random vessel effects and random | |||
stratum-by-year effects. | |||
CCAMLR Science. 11: 59--80.</ref> | |||
* [[Mertens function]] <ref name="Kendal2011a" /> | |||
==References== | |||
{{reflist}} | |||
== Further reading == | |||
* Kaas, R. (2005). [http://ucs.kuleuven.be/seminars_events/other/files/3afmd/Kaas.PDF "Compound Poisson distribution and GLM’s – Tweedie’s distribution"]. In ''Proceedings of the Contact Forum "3rd Actuarial and Financial Mathematics Day"'', pages 3–12. Brussels: Royal Flemish Academy of Belgium for Science and the Arts. | |||
* Ohlsson, E and Johansson, B. (2003) [http://www.math.su.se/matstat/reports/seriea/2003/rep15/report.pdf ''Exact Credibility and Tweedie Models''], University of Stockholm, Research report, October 2003. | |||
* Tweedie, M.C.K. (1956). "Some statistical properties of inverse Gaussian distributions". ''Virginia J. Sci. (N.S.)'' 7, 160—165. | |||
==External links== | |||
* Tweedie distributions. http://www.statsci.org/s/tweedie.html | |||
* Tweedie generalized linear model family. http://www.statsci.org/s/tweedief.html | |||
* Examples of use of the model. http://www.sci.usq.edu.au/staff/dunn/Datasets/tech-glms.html#Tweedie | |||
* tweeDEseq: R package for RNA-seq data analysis using the Poisson-Tweedie family of distributions. http://bioconductor.org/packages/2.9/bioc/html/tweeDEseq.html | |||
{{ProbDistributions|families}} | |||
[[Category:Continuous distributions|continuous distributions]] | |||
[[Category:Probability distributions]] | |||
[[Category:Systems of probability distributions]] |
Revision as of 17:27, 15 June 2013
In probability and statistics, the Tweedie distributions are a family of probability distributions which include the purely continuous normal and gamma distributions, the purely discrete scaled Poisson distribution, and the class of mixed compound Poisson–gamma distributions which have positive mass at zero, but are otherwise continuous.[1] For any random variable Y that obeys a Tweedie distribution, the variance var(Y) relates to the mean E(Y) by the power law,
where a and p are positive constants.
The Tweedie distributions were named by Bent Jørgensen[2] after Maurice Tweedie, a statistician and medical physicist at the University of Liverpool, UK, who presented the first thorough study of these distributions in 1984.[1][3]
Examples
The Tweedie distributions include a number of familiar distributions as well as some unusual ones, each being specified by the domain of the index parameter. We have the
- normal distribution, p=0,
- Poisson distribution, p=1,
- compound Poisson–gamma distribution, 1<p<2,
- gamma distribution, p=2,
- positive stable distributions, 2<p<3,
- positive stable distributions, p>3, and
- extreme stable distributions, p=Buying, selling and renting HDB and personal residential properties in Singapore are simple and transparent transactions. Although you are not required to engage a real property salesperson (generally often known as a "public listed property developers In singapore agent") to complete these property transactions, chances are you'll think about partaking one if you are not accustomed to the processes concerned.
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For 0<p<1 no Tweedie model exists.
Definitions
Tweedie distributions are a special case of exponential dispersion models, a class of models used to describe error distributions for the generalized linear model.[4] The term exponential dispersion model refers to the exponential form that these models take, evident from the canonical equation used to describe the distribution Pλ,θ of the random variable Z on the measurable sets A,
with the interrelated measures νλ. θ is the canonical parameter; the cumulant function is
λ is the index parameter; and z the canonical statistic. This equation represents a family of exponential dispersion models ED*(θ,λ) that are completely determined by the parameters θ and λ and the cumulant function.
Additive exponential dispersion models
The models just described are additive models with the property that the distribution of the sum of independent random variables,
for which Zi~ED*(θ,λi) with fixed θ and various λ are members of the family of distributions with the same θ,
Reproductive exponential dispersion models
A second class of exponential dispersion models exists designated by the random variable
where σ2=1/λ, known as reproductive exponential dispersion models. They have the property that for n independent random variables Yi~ED(μ,σ2/wi), with weighting factors wi and
a weighted average of the variables gives,
For reproductive models the weighted average of independent random variables with fixed μ and σ2 and various values for wi is a member of the family of distributions with same μ and σ2.
The Tweedie exponential dispersion models are both additive and reproductive; we thus have the duality transformation
Scale invariance
A third property of the Tweedie models is that they are scale invariant: For a reproductive exponential dispersion model ED(μ,σ2) and any positive constant c we have the property of closure under scale transformation,
where the index parameter p is a real-valued unitless constant. With this transformation the new variable Y’=cY belongs to the family of distributions with fixed μ and σ2 but different values of c.
The Tweedie power variance function
To define the variance function for exponential dispersion models we make use of the mean value mapping, the relationship between the canonical parameter θ and the mean μ. It is define by the function
The variance function V(μ) is constructed from the mean value mapping,
Here the minus exponent in τ -1(μ) denotes an inverse function rather than a reciprocal. The mean and variance of an additive random variable is then E(Z)=λμ and var(Z)=λV(μ).
Scale invariance implies that the variance function obeys the relationship V(μ)=μ p.[4]
The Tweedie cumulant generating functions
The properties of exponential dispersion models give us two differential equations.[4] The first relates the mean value mapping and the variance function to each other,
The second shows how the mean value mapping is related to the cumulant function,
These equations can be solved to obtain the cumulant function for different cases of the Tweedie models. A cumulant generating function (CGF) may then be obtained from the cumulant function. The additive CGF is generally specified by the equation
and the reproductive CGF by
where s is the generating function variable.
The cumulant functions for specific values of the index parameter p are[4]
where α is the Tweedie exponent
For the additive Tweedie models the CGFs take the form,
and for the reproductive models,
The additive and reproductive Tweedie models are conventionally denoted by the symbols Tw*p(θ,λ) and Twp(θ,σ2), respectively.
The first and second derivatives of the CGFs, with s=0, yields the mean and variance, respectively. One can thus confirm that for the additive models the variance relates to the mean by the power law,
The Tweedie convergence theorem
The Tweedie exponential dispersion models are fundamental in statistical theory consequent to their roles as foci of convergence for a wide range of statistical processes. Jørgensen et al proved a theorem that specifies the asymptotic behaviour of variance functions known as the Tweedie convergence theorem".[5] This theorem, in technical terms, is stated thus:[4] The unit variance function is regular of order p at zero (or infinity) provided that V(μ)~c0μp for μ as it approaches zero (or infinity) for all real values of p and c0 >0. Then for a unit variance function regular of order p at either zero or infinity and for
as or , respectively, where the convergence is through values of c such that cμ is in the domain of θ and cp-2/σ2 is in the domain of λ. The model must be infinitely divisible as c2-p approaches infinity.[4]
In nontechnical terms this theorem implies that any exponential dispersion model that asymptotically manifests a variance-to-mean power law is required to have a variance function that comes within the domain of attraction of a Tweedie model. Almost all distribution functions with finite cumulant generating functions qualify as exponential dispersion models and most exponential dispersion models manifest variance functions of this form. Hence many probability distributions have variance functions that express this asymptotic behavior, and the Tweedie distributions become foci of convergence for a wide range of data types.[6]
The Tweedie models and Taylor’s power law
Taylor's law is an empirical law in ecology that relates the variance of the number of individuals of a species per unit area of habitat to the corresponding mean by a power-law relationship.[7] For the population count Y with mean µ and variance var(Y), Taylor’s law is written,
where a and p are both positive constants. Since L. R. Taylor described this law in 1961 there have been many different explanations offered to explain it, ranging from animal behavior,[7] a random walk model,[8] a stochastic birth, death, immigration and emigration model,[9] to a consequence of equilibrium and non-equilibrium statistical mechanics.[10] No consensus exists as to an explanation for this model.
Since Taylor’s law is mathematically identical to the variance-to-mean power law that characterizes the Tweedie models, it seemed reasonable to use these models and the Tweedie convergence theorem to explain the observed clustering of animals and plants associated with Taylor’s law.[11][12] The majority of the observed values for the power-law exponent p have fallen in the interval (1,2) and so the Tweedie compound Poisson–gamma distribution would seem applicable. Comparison of the empirical distribution function to the theoretical compound Poisson–gamma distribution has provided a means to verify consistency of this hypothesis.[11]
Whereas conventional models for Taylor’s law have tended to involve ad hoc animal behavioral or population dynamic assumptions, the Tweedie convergence theorem would imply that Taylor’s law results from a general mathematical convergence effect much as how the central limit theorem governs the convergence behavior of certain types of random data. Indeed, any mathematical model, approximation or simulation that is designed to yield Taylor’s law (on the basis of this theorem) is required to converge to the form of the Tweedie models.[6]
The double power law
The eponym Taylor's power law has been applied to a wide range of data that manifests a variance-to-mean power function. However, subtle mathematical differences exist between the transformational properties of some of these data. A double power law, which includes Taylor’s original law, has been proposed to describe these differences.[13] For a population count drawn from an area of size t with mean abundance per unit area µ, and where
we have for the double power law:
The constant dBuying, selling and renting HDB and personal residential properties in Singapore are simple and transparent transactions. Although you are not required to engage a real property salesperson (generally often known as a "public listed property developers In singapore agent") to complete these property transactions, chances are you'll think about partaking one if you are not accustomed to the processes concerned.
Professional agents are readily available once you need to discover an condominium for hire in singapore In some cases, landlords will take into account you more favourably in case your agent comes to them than for those who tried to method them by yourself. You need to be careful, nevertheless, as you resolve in your agent. Ensure that the agent you are contemplating working with is registered with the IEA – Institute of Estate Brokers. Whereas it might sound a hassle to you, will probably be worth it in the end. The IEA works by an ordinary algorithm and regulations, so you'll protect yourself in opposition to probably going with a rogue agent who prices you more than they should for his or her service in finding you an residence for lease in singapore.
There isn't any deal too small. Property agents who are keen to find time for any deal even if the commission is small are the ones you want on your aspect. Additionally they present humbleness and might relate with the typical Singaporean higher. Relentlessly pursuing any deal, calling prospects even without being prompted. Even if they get rejected a hundred times, they still come again for more. These are the property brokers who will find consumers what they need eventually, and who would be the most successful in what they do. 4. Honesty and Integrity
This feature is suitable for you who need to get the tax deductions out of your PIC scheme to your property agency firm. It's endorsed that you visit the correct site for filling this tax return software. This utility must be submitted at the very least yearly to report your whole tax and tax return that you're going to receive in the current accounting 12 months. There may be an official website for this tax filling procedure. Filling this tax return software shouldn't be a tough thing to do for all business homeowners in Singapore.
A wholly owned subsidiary of SLP Worldwide, SLP Realty houses 900 associates to service SLP's fast rising portfolio of residential tasks. Real estate is a human-centric trade. Apart from offering comprehensive coaching applications for our associates, SLP Realty puts equal emphasis on creating human capabilities and creating sturdy teamwork throughout all ranges of our organisational hierarchy. Worldwide Presence At SLP International, our staff of execs is pushed to make sure our shoppers meet their enterprise and investment targets. Under is an inventory of some notable shoppers from completely different industries and markets, who've entrusted their real estate must the expertise of SLP Worldwide.
If you're looking for a real estate or Singapore property agent online, you merely need to belief your instinct. It is because you don't know which agent is sweet and which agent will not be. Carry out research on a number of brokers by looking out the internet. As soon as if you find yourself certain that a selected agent is dependable and trustworthy, you'll be able to choose to utilize his partnerise find you a house in Singapore. More often than not, a property agent is considered to be good if she or he places the contact data on his web site. This is able to imply that the agent does not thoughts you calling them and asking them any questions regarding properties in Singapore. After chatting with them you too can see them of their office after taking an appointment.
Another method by way of which you could find out whether the agent is sweet is by checking the feedback, of the shoppers, on the website. There are various individuals would publish their comments on the web site of the Singapore property agent. You can take a look at these feedback and the see whether it will be clever to hire that specific Singapore property agent. You may even get in contact with the developer immediately. Many Singapore property brokers know the developers and you may confirm the goodwill of the agent by asking the developer. [0,1] has been identified as a fractal exponent. The factor aµ p represents the original Taylor’s law, a function of the mean abundance per unit area; the last term t2-d describes how the power law scales with the enumerative bin size. This last term implies a statistically self-similar scaling of the spatial distribution of items of interest as the size of the bin changes. It is this second portion of the double power law that underlies the variance-to-mean power law reported in systems like regional blood flow heterogeneity,[14] the genomic distribution of SNPs[15] and genes,[16] and number theoretic examples.[6][17]
Tweedie convergence and 1/f noise
Pink noise, or 1/f noise, refers to a pattern of noise characterized by a power-law relationship between its intensities S(f) at different frequencies f,
where the dimensionless exponent γBuying, selling and renting HDB and personal residential properties in Singapore are simple and transparent transactions. Although you are not required to engage a real property salesperson (generally often known as a "public listed property developers In singapore agent") to complete these property transactions, chances are you'll think about partaking one if you are not accustomed to the processes concerned.
Professional agents are readily available once you need to discover an condominium for hire in singapore In some cases, landlords will take into account you more favourably in case your agent comes to them than for those who tried to method them by yourself. You need to be careful, nevertheless, as you resolve in your agent. Ensure that the agent you are contemplating working with is registered with the IEA – Institute of Estate Brokers. Whereas it might sound a hassle to you, will probably be worth it in the end. The IEA works by an ordinary algorithm and regulations, so you'll protect yourself in opposition to probably going with a rogue agent who prices you more than they should for his or her service in finding you an residence for lease in singapore.
There isn't any deal too small. Property agents who are keen to find time for any deal even if the commission is small are the ones you want on your aspect. Additionally they present humbleness and might relate with the typical Singaporean higher. Relentlessly pursuing any deal, calling prospects even without being prompted. Even if they get rejected a hundred times, they still come again for more. These are the property brokers who will find consumers what they need eventually, and who would be the most successful in what they do. 4. Honesty and Integrity
This feature is suitable for you who need to get the tax deductions out of your PIC scheme to your property agency firm. It's endorsed that you visit the correct site for filling this tax return software. This utility must be submitted at the very least yearly to report your whole tax and tax return that you're going to receive in the current accounting 12 months. There may be an official website for this tax filling procedure. Filling this tax return software shouldn't be a tough thing to do for all business homeowners in Singapore.
A wholly owned subsidiary of SLP Worldwide, SLP Realty houses 900 associates to service SLP's fast rising portfolio of residential tasks. Real estate is a human-centric trade. Apart from offering comprehensive coaching applications for our associates, SLP Realty puts equal emphasis on creating human capabilities and creating sturdy teamwork throughout all ranges of our organisational hierarchy. Worldwide Presence At SLP International, our staff of execs is pushed to make sure our shoppers meet their enterprise and investment targets. Under is an inventory of some notable shoppers from completely different industries and markets, who've entrusted their real estate must the expertise of SLP Worldwide.
If you're looking for a real estate or Singapore property agent online, you merely need to belief your instinct. It is because you don't know which agent is sweet and which agent will not be. Carry out research on a number of brokers by looking out the internet. As soon as if you find yourself certain that a selected agent is dependable and trustworthy, you'll be able to choose to utilize his partnerise find you a house in Singapore. More often than not, a property agent is considered to be good if she or he places the contact data on his web site. This is able to imply that the agent does not thoughts you calling them and asking them any questions regarding properties in Singapore. After chatting with them you too can see them of their office after taking an appointment.
Another method by way of which you could find out whether the agent is sweet is by checking the feedback, of the shoppers, on the website. There are various individuals would publish their comments on the web site of the Singapore property agent. You can take a look at these feedback and the see whether it will be clever to hire that specific Singapore property agent. You may even get in contact with the developer immediately. Many Singapore property brokers know the developers and you may confirm the goodwill of the agent by asking the developer. [0,1]. It is found within a diverse number of natural processes.[18] Many different explanations for 1/f noise exist, a widely held hypothesis is based on Self-organized criticality where dynamical systems close to a critical point are thought to manifest scale-invariant spatial and/or temporal behavior.
In this subsection a mathematical connection between 1/f noise and the Tweedie variance-to-mean power law will be described. To begin, we first need to introduce self-similar processes: For the sequence of numbers
with mean
deviations
variance
and autocorrelation function
with lag k, if the autocorrelation of this sequence has the long range behavior
as kBuying, selling and renting HDB and personal residential properties in Singapore are simple and transparent transactions. Although you are not required to engage a real property salesperson (generally often known as a "public listed property developers In singapore agent") to complete these property transactions, chances are you'll think about partaking one if you are not accustomed to the processes concerned.
Professional agents are readily available once you need to discover an condominium for hire in singapore In some cases, landlords will take into account you more favourably in case your agent comes to them than for those who tried to method them by yourself. You need to be careful, nevertheless, as you resolve in your agent. Ensure that the agent you are contemplating working with is registered with the IEA – Institute of Estate Brokers. Whereas it might sound a hassle to you, will probably be worth it in the end. The IEA works by an ordinary algorithm and regulations, so you'll protect yourself in opposition to probably going with a rogue agent who prices you more than they should for his or her service in finding you an residence for lease in singapore.
There isn't any deal too small. Property agents who are keen to find time for any deal even if the commission is small are the ones you want on your aspect. Additionally they present humbleness and might relate with the typical Singaporean higher. Relentlessly pursuing any deal, calling prospects even without being prompted. Even if they get rejected a hundred times, they still come again for more. These are the property brokers who will find consumers what they need eventually, and who would be the most successful in what they do. 4. Honesty and Integrity
This feature is suitable for you who need to get the tax deductions out of your PIC scheme to your property agency firm. It's endorsed that you visit the correct site for filling this tax return software. This utility must be submitted at the very least yearly to report your whole tax and tax return that you're going to receive in the current accounting 12 months. There may be an official website for this tax filling procedure. Filling this tax return software shouldn't be a tough thing to do for all business homeowners in Singapore.
A wholly owned subsidiary of SLP Worldwide, SLP Realty houses 900 associates to service SLP's fast rising portfolio of residential tasks. Real estate is a human-centric trade. Apart from offering comprehensive coaching applications for our associates, SLP Realty puts equal emphasis on creating human capabilities and creating sturdy teamwork throughout all ranges of our organisational hierarchy. Worldwide Presence At SLP International, our staff of execs is pushed to make sure our shoppers meet their enterprise and investment targets. Under is an inventory of some notable shoppers from completely different industries and markets, who've entrusted their real estate must the expertise of SLP Worldwide.
If you're looking for a real estate or Singapore property agent online, you merely need to belief your instinct. It is because you don't know which agent is sweet and which agent will not be. Carry out research on a number of brokers by looking out the internet. As soon as if you find yourself certain that a selected agent is dependable and trustworthy, you'll be able to choose to utilize his partnerise find you a house in Singapore. More often than not, a property agent is considered to be good if she or he places the contact data on his web site. This is able to imply that the agent does not thoughts you calling them and asking them any questions regarding properties in Singapore. After chatting with them you too can see them of their office after taking an appointment.
Another method by way of which you could find out whether the agent is sweet is by checking the feedback, of the shoppers, on the website. There are various individuals would publish their comments on the web site of the Singapore property agent. You can take a look at these feedback and the see whether it will be clever to hire that specific Singapore property agent. You may even get in contact with the developer immediately. Many Singapore property brokers know the developers and you may confirm the goodwill of the agent by asking the developer. and where L(k) is a slowly varying function at large values of k, this sequence is called a self-similar process.[19]
The method of expanding bins can be used to analyze self-similar processes. Consider a set of equal-sized non-overlapping bins that divides the original sequence of N elements into groups of m equal-sized segments (N/m is integer) so that new reproductive sequences, based on the mean values, can be defined:
The variance determined from this sequence will scale as the bin size changes such that
if and only if the autocorrelation has the limiting form[20]
One can also construct a set of corresponding additive sequences
based on the expanding bins,
Provided the autocorrelation function exhibits the same behavior, the additive sequences will obey the relationship
Since and are constants this relationship constitutes a variance-to-mean power law, with p=2-d.[6][21]
The biconditional relationship above between the variance-to-mean power law and power law autocorrelation function, and the Wiener–Khinchin theorem[22] imply that any sequence that exhibits a variance-to-mean power law by the method of expanding bins will also manifest 1/f noise, and vice versa. Moreover, the Tweedie convergence theorem, by virtue of its central limit-like effect of generating distributions that manifest variance-to-mean power functions, will also generate processes that manifest 1/f noise.[6] The Tweedie convergence theorem thus allows provides an alternative explanation for the origin of 1/f noise, based its central limit-like effect.
Much as the central limit theorem requires certain kinds of random processes to have as a focus of their convergence the Gaussian distribution and thus express white noise, the Tweedie convergence theorem requires certain non-Gaussian processes to have as a focus of convergence the Tweedie distributions that express 1/f noise.[6]
The Tweedie models and multifractality
From the properties of self-similar processes, the power-law exponent p=2-d is related to the Hurst exponent H and the fractal dimension D by[20]
A one-dimensional data sequence of self-similar data may demonstrate a variance-to-mean power law with local variations in the value of p and hence in the value of D. When fractal structures manifest local variations in fractal dimension, they are said to be multifractals. Examples of data sequences that exhibit local variations in p like this include the eigenvalue deviations of the Gaussian Orthogonal and Unitary Ensembles.[6] The Tweedie compound Poisson–gamma distribution has served to model multifractality based on local variations in the Tweedie exponent α. Consequently, in conjunction with the variation of α, the Tweedie convergence theorem can be viewed as having a role in the genesis of such multifractals.
The variation of α has been found to obey the asymmetric Laplace distribution in certain cases. [23] This distribution has been shown to be a member of the family of geometric Tweedie models [13], that manifest as limiting distributions in a convergence theorem for geometric dispersion models.
Applications
Regional organ blood flow
Regional organ blood flow has been traditionally assessed by the injection of radiolabelled polyethylene microspheres into the arterial circulation of animals, of a size that they become entrapped within the microcirculation of organs. The organ to be assessed is then divided into equal-sized cubes and the amount of radiolabel within each cube is evaluated by liquid scintillation counting and recorded. The amount of radioactivity within each cube is taken to reflect the blood flow through that sample at the time of injection. It is possible to evaluate adjacent cubes from an organ in order to additively determine the blood flow through larger regions. Through the work of J B Bassingthwaighte and others an empirical power law has been derived between the relative dispersion of blood flow of tissue samples (RD=standard deviation/ mean)of mass m relative to reference sized samples:[24]
This power law exponent Ds has been called a fractal dimension. Bassingthwaighte’s power law can be shown to directly relate to the variance-to-mean power law. Regional organ blood flow can thus be modelled by the Tweedie compound Poisson–gamma distribution.[14] In this model tissue sample could be considered to contain a random (Poisson) distributed number of entrapment sites, each with gamma distributed blood flow. Blood flow at this microcirculatory level has been observed to obey a gamma distribution,[25] thus providing support for this hypothesis.
Cancer metastasis
The "experimental cancer metastasis assay"[26] has some resemblance to the above method to measure regional blood flow. Groups of syngeneic and age matched mice are given intravenous injections of equal-sized aliquots of suspensions of cloned cancer cells and then after a set period of time their lungs are removed and the number of cancer metastases enumerated within each pair of lungs. If other groups of mice are injected with different cancer cell clones then the number of metastases per group will differ in accordance with the metastatic potentials of the clones. It has been long recognized that there can be considerable intraclonal variation in the numbers of metastases per mouse despite the best attempts to keep the experimental conditions within each clonal group uniform.[26] This variation is larger than would be expected on the basis of a Poisson distribution of numbers of metastases per mouse in each clone and when the variance of the number of metastases per mouse was plotted against the corresponding mean a power law was found.[27]
The variance-to-mean power law for metastases was found to also hold for spontaneous murine metastases[28] and for cases series of human metastases.[29] Since hematogenous metastasis occurs in direct relationship to regional blood flow[30] and videomicroscopic studies indicate that the passage and entrapment of cancer cells within the circulation appears analogous to the microsphere experiments[31] it seemed plausible to propose that the variation in numbers of hematogenous metastases could reflect heterogeneity in regional organ blood flow.[32] The blood flow model was based on the Tweedie compound Poisson–gamma distribution, a distribution governing a continuous random variable. For that reason in the metastasis model it was assumed that blood flow was governed by that distribution and that the number of regional metastases occurred as a Poisson process for which the intensity was directly proportional to blood flow. This lead to the description of the Poisson negative binomial (PNB) distribution as a discrete equivalent to the Tweedie compound Poisson–gamma distribution. The probability generating function for the PNB distribution is
The relationship between the mean and variance of the PNB distribution is then
which, in the range of many experimental metastasis assays, would be indistinguishable from the variance-to-mean power law. For sparse data, however, this discrete variance-to-mean relationship would behave more like that of a Poisson distribution where the variance equaled the mean.
Genomic structure and evolution
The local density of Single Nucleotide Polymorphisms (SNPs) within the human genome, as well as that of genes, appears to cluster in accord with the variance-to-mean power law and the Tweedie compound Poisson–gamma distribution.[15][16] In the case of SNPs their observed density reflects the assessment techniques, the availability of genomic sequences for analysis, and the nucleotide heterozygosity.[33] The first two factors reflect ascertainment errors inherent to the collection methods, the latter factor reflects an intrinsic property of the genome.
In the coalescent model of population genetics each genetic locus has its own unique history. Within the evolution of a population from some species some genetic loci could presumably be traced back to a relatively recent common ancestor whereas other loci might have more ancient genealogies. More ancient genomic segments would have had more time to accumulate SNPs and to experience recombination. R R Hudson has proposed a model where recombination could cause variation in the time to most common recent ancestor for different genomic segments.[34] A high recombination rate could cause a chromosome to contain a large number of small segments with less correlated genealogies.
Assuming a constant background rate of mutation the number of SNPs per genomic segment would accumulate proportionately to the time to the most recent common ancestor. Current population genetic theory would indicate that these times would be gamma distributed, on average.[35] The Tweedie compound Poisson–gamma distribution would suggest a model whereby the SNP map would consist of multiple small genomic segments with the mean number of SNPs per segment would be gamma distributed as per Hudson’s model.
The distribution of genes within the human genome also demonstrated a variance-to-mean power law, when the method of expanding bins was used to determine the corresponding variances and means.[16] Similarly the number of genes per enumerative bin was found to obey a Tweedie compound Poisson–gamma distribution. This probability distribution was deemed compatible with two different biological models: the microarrangement model where the number of genes per unit genomic length was determined by the sum of a random number of smaller genomic segments derived by random breakage and reconstruction of protochormosomes. These smaller segments would be assumed to carry on average a gamma distributed number of genes.
In the alternative gene cluster model, genes would be distributed randomly within the protochromosomes. Over large evolutionary timescales there would occur tandem duplication, mutations, insertions, deletions and rearrangements that could affect the genes through a stochastic birth, death and immigration process to yield the Tweedie compound Poisson–gamma distribution.
Both these mechanisms would implicate neutral evolutionary processes that would result in regional clustering of genes.
Random matrix theory
The Gaussian unitary ensemble (GUE) consists of complex Hermitian matrices that are invariant under unitary transformations whereas the Gaussian orthogonal ensemble (GOE) consists of real symmetric matrices invariant under orthogonal transformations. The ranked eigenvalues En from these random matrices obey Wigner’s semicircular distribution: For a NxN matrix the average density for eigenvalues of size E will be
as EBuying, selling and renting HDB and personal residential properties in Singapore are simple and transparent transactions. Although you are not required to engage a real property salesperson (generally often known as a "public listed property developers In singapore agent") to complete these property transactions, chances are you'll think about partaking one if you are not accustomed to the processes concerned.
Professional agents are readily available once you need to discover an condominium for hire in singapore In some cases, landlords will take into account you more favourably in case your agent comes to them than for those who tried to method them by yourself. You need to be careful, nevertheless, as you resolve in your agent. Ensure that the agent you are contemplating working with is registered with the IEA – Institute of Estate Brokers. Whereas it might sound a hassle to you, will probably be worth it in the end. The IEA works by an ordinary algorithm and regulations, so you'll protect yourself in opposition to probably going with a rogue agent who prices you more than they should for his or her service in finding you an residence for lease in singapore.
There isn't any deal too small. Property agents who are keen to find time for any deal even if the commission is small are the ones you want on your aspect. Additionally they present humbleness and might relate with the typical Singaporean higher. Relentlessly pursuing any deal, calling prospects even without being prompted. Even if they get rejected a hundred times, they still come again for more. These are the property brokers who will find consumers what they need eventually, and who would be the most successful in what they do. 4. Honesty and Integrity
This feature is suitable for you who need to get the tax deductions out of your PIC scheme to your property agency firm. It's endorsed that you visit the correct site for filling this tax return software. This utility must be submitted at the very least yearly to report your whole tax and tax return that you're going to receive in the current accounting 12 months. There may be an official website for this tax filling procedure. Filling this tax return software shouldn't be a tough thing to do for all business homeowners in Singapore.
A wholly owned subsidiary of SLP Worldwide, SLP Realty houses 900 associates to service SLP's fast rising portfolio of residential tasks. Real estate is a human-centric trade. Apart from offering comprehensive coaching applications for our associates, SLP Realty puts equal emphasis on creating human capabilities and creating sturdy teamwork throughout all ranges of our organisational hierarchy. Worldwide Presence At SLP International, our staff of execs is pushed to make sure our shoppers meet their enterprise and investment targets. Under is an inventory of some notable shoppers from completely different industries and markets, who've entrusted their real estate must the expertise of SLP Worldwide.
If you're looking for a real estate or Singapore property agent online, you merely need to belief your instinct. It is because you don't know which agent is sweet and which agent will not be. Carry out research on a number of brokers by looking out the internet. As soon as if you find yourself certain that a selected agent is dependable and trustworthy, you'll be able to choose to utilize his partnerise find you a house in Singapore. More often than not, a property agent is considered to be good if she or he places the contact data on his web site. This is able to imply that the agent does not thoughts you calling them and asking them any questions regarding properties in Singapore. After chatting with them you too can see them of their office after taking an appointment.
Another method by way of which you could find out whether the agent is sweet is by checking the feedback, of the shoppers, on the website. There are various individuals would publish their comments on the web site of the Singapore property agent. You can take a look at these feedback and the see whether it will be clever to hire that specific Singapore property agent. You may even get in contact with the developer immediately. Many Singapore property brokers know the developers and you may confirm the goodwill of the agent by asking the developer.. Integration of the semicircular rule provides the number of eigenvalues on average less than E,
The ranked eigenvalues can be unfolded, or renormalized, with the equation
This removes the trend of the sequence from the fluctuating portion. If we look at the absolute value of the difference between the actual and expected cumulative number of eigenvalues
we obtain a sequence of eigenvalue fluctuations which, using the method of expanding bins, reveals a variance-to-mean power law.[6] The eigenvalue fluctuations of both the GUE and the GOE manifest this power law with the power law exponents ranging between 1 and 2, and they similarly manifest 1/f noise spectra. These eigenvalue fluctuations also correspond to the Tweedie compound Poisson–gamma distribution and they exhibit multifractality.[6]
The distribution of prime numbers
The second Chebyshev function ψ(x) is given by,
where the summation extends over all prime powers not exceeding x, x runs over the positive real numbers, and is the von Mangoldt function. The function ψ(x) is related to the prime-counting function π(x), and as such provides information with regards to the distribution of prime numbers amongst the real numbers. It is asymptotic to x, a statement equivalent to the prime number theorem and it can also be shown to be related to the zeros of the Riemann zeta function located on the critical strip ρ, where the real part of the zeta zero ρ is between 0 and 1. Then ψ expressed for x greater than one can be written:
where
The Riemann hypothesis states that the nontrivial zeros of the Riemann zeta function all have real part ½. These zeta function zeros are related to the distribution of prime numbers. Schoenfeld[36] has shown that if the Riemann hypothesis is true then
for all . If we analyze the Chebyshev deviations Δ (n) on the integers n using the method of expanding bins and plot the variance versus the mean a variance to mean power law can be demonstrated.[37] Moreover, these deviations correspond to the Tweedie compound Poisson-gamma distribution and they exhibit 1/f noise.
Other applications
Applications of Tweedie distributions include:
- actuarial studies[38][39][40][41][42][43][44]
- assay analysis [45][46]
- survival analysis[47][48][49]
- ecology [11]
- analysis of alcohol consumption in British teenagers [50]
- medical applications [51]
- meteorology and climatology [51][52]
- fisheries [53]
- Mertens function [17]
References
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.
Further reading
- Kaas, R. (2005). "Compound Poisson distribution and GLM’s – Tweedie’s distribution". In Proceedings of the Contact Forum "3rd Actuarial and Financial Mathematics Day", pages 3–12. Brussels: Royal Flemish Academy of Belgium for Science and the Arts.
- Ohlsson, E and Johansson, B. (2003) Exact Credibility and Tweedie Models, University of Stockholm, Research report, October 2003.
- Tweedie, M.C.K. (1956). "Some statistical properties of inverse Gaussian distributions". Virginia J. Sci. (N.S.) 7, 160—165.
External links
- Tweedie distributions. http://www.statsci.org/s/tweedie.html
- Tweedie generalized linear model family. http://www.statsci.org/s/tweedief.html
- Examples of use of the model. http://www.sci.usq.edu.au/staff/dunn/Datasets/tech-glms.html#Tweedie
- tweeDEseq: R package for RNA-seq data analysis using the Poisson-Tweedie family of distributions. http://bioconductor.org/packages/2.9/bioc/html/tweeDEseq.html
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The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ 4.0 4.1 4.2 4.3 4.4 4.5 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 Cite error: Invalid<ref>
tag; name "Jørgensen-1997" defined multiple times with different content - ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Template:Cite doi Cite error: Invalid
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tag; name "Kendal2011b" defined multiple times with different content - ↑ 7.0 7.1 Taylor LR (1961) Aggregation, variance and the mean. Nature 189, 732–735
- ↑ Hanski I (1980) Spatial patterns and movements in coprophagous beetles. Oikos 34, 293-310
- ↑ Anderson RD, Crawley GM & Hassell M (1982) Variability in the abundance of animal and plant species. Nature 296, 245–248
- ↑ Fronczak A & Fronczak P (2010) Origins of Taylor’s power law for fluctuation scaling in complex systems. Phys Rev E 81, 066112
- ↑ 11.0 11.1 11.2 Kendal WS (2002) Spatial aggregation of the Colorado potato beetle described by an exponential dispersion model. Ecological Modelling 151, 261–269 Cite error: Invalid
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tag; name "Kendal2002" defined multiple times with different content - ↑ Kendal WS (2004) Taylor’s ecological power law as a consequence of scale invariant exponential dispersion models. Ecol Complex 1, 193–209
- ↑ 13.0 13.1 Jørgensen B, Martinez JR & Demetrio CGB (2011) Self-similarity and Lamperti convergence for families of stochastic processes. Lith Math J 51, 342–362 Cite error: Invalid
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tag; name "Jørgensen2011" defined multiple times with different content - ↑ 14.0 14.1 Kendal WS (2001) A stochastic model for the self-similar heterogeneity of regional organ blood flow. Proc Natl Acad Sci U S A 98, 837-841
- ↑ 15.0 15.1 Kendal WS (2003) An exponential dispersion model for the distribution of human single nucleotide polymorphisms" Mol Biol Evol 20 579-590
- ↑ 16.0 16.1 16.2 One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ 17.0 17.1 Kendal WS & Jørgensen B (2011) Taylor's power law and fluctuation scaling explained by a central-limit-like convergence. Phys. Rev. E 83,066115
- ↑ Dutta P & Horn PM (1981) Low frequency fluctuations in solids: 1/f noise. Rev Mod Phys 53,497-516
- ↑ Leland WE, Taqqu MS, Willinger W & Wilson DV (1994) On the self-similar nature of ethernet traffic. IEE/ACM Trans Networking 2, 1-15
- ↑ 20.0 20.1 Tsybakov B & Georganas ND (1997) On self-similar traffic in ATM queues: definitions, overflow probability bound, and cell delay distribution. IEEE/ACM Trans Networking 5, 397–409
- ↑ Kendal WS (2007) Scale invariant correlations between genes and SNPs on Human chromosome 1 reveal potential evolutionary mechanisms. J Theor Biol 245, 329-340
- ↑ McQuarrie DA (1976) Statistical mechanics [Harper & Row]
- ↑ Kendal WS (2014) Multifractality attributed to dual central limit-lie convergence effects. Physica A 401, 22-33
- ↑ Bassingthwaighte JB (1989) Fractal nature of regional myocardial blood flow heterogeneity. Circ Res 65, 578-590
- ↑ Honig CR, Feldstein ML, Frierson JL. 1977. Capillary lengths, anastomoses, and estimated capillary transit times in skeletal muscle. Am J Physiol Heart Circul Physiol 233: H122--H129.
- ↑ 26.0 26.1 One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang Cite error: Invalid<ref>
tag; name "Fidler1977" defined multiple times with different content - ↑ Kendal WS & Frost P (1987) Experimental metastasis: a novel application of the variance-to-mean power function. J Natl Cancer Inst 79, 1113-1115
- ↑ Kendal WS. 1999. Clustering of murine lung metastases reflects fractal nonuniformity in regional lung blood flow. Invasion Metastasis 18: 285--296.
- ↑ Kendal WS, Lagerwaard, FJ & Agboola O. 2000. Characterization of the frequency distribution for human hematogenous metastases: evidence for clustering and a power variance function. Clin Exp Metastasis 18: 219--229.
- ↑ Weiss L, Bronk J, Pickren JW & Lane WW. 1981. Metastatic patterns and targe organ arterial blood flow. Invasion Metastasis 1: 126--135.
- ↑ Chambers AF, Groom AC & MacDonald IC. 2002. Dissemination and growth of cancer cells in metastatic sites. Nature Rev Cancer 2: 563--572.
- ↑ Kendal WS. 2002. A frequency distribution for the number of hematogenous organ metastases. Invasion Metastasis 1: 126--135.
- ↑ The international SNP map working group. 2001. A map of human genome variation containing 1.42 million single nucleotide polymorphisms" Nature 409: 928--933.
- ↑ Hudson RR. 1991. Gene genealogies and the coalescent process. Oxford surveys in evolutionary biology 7: 1--44.
- ↑ Tavare S, Balding DJ, Griffiths RC & Donnelly P. 1997. Inferring coalescent times from DNA sequence data" Genetics 145: 505--518.
- ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ Haberman, S. and Renshaw, A. E. 1996. Generalized linear models and actuarial science. The Statistician, 45: 407--436.
- ↑ Renshaw, A. E. 1994. Modelling the claims process in the presence of covariates. ASTIN Bulletin 24: 265--286.
- ↑ Jørgensen, B. and Paes de Souza, M. C. 1994. Fitting Tweedie's compound Poisson model to insurance claims data. Scand. Actuar. J. 1: 69--93.
- ↑ Haberman, S., and Renshaw, A. E. 1998. Actuarial applications of generalized linear models. In Statistics in Finance, D. J. Hand and S. D. Jacka (eds), Arnold, London.
- ↑ Mildenhall, S. J. 1999. A systematic relationship between minimum bias and generalized linear models. 1999 Proceedings of the Casualty Actuarial Society 86: 393--487.
- ↑ Murphy, K. P., Brockman, M. J., and Lee, P. K. W. (2000). Using generalized linear models to build dynamic pricing systems. Casualty Actuarial Forum, Winter 2000.
- ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ Davidian, M. 1990. Estimation of variance functions in assays with possible unequal replication and nonnormal data. Biometrika 77: 43--54.
- ↑ Davidian, M., Carroll, R. J. and Smith, W. 1988. Variance functions and the minimum detectable concentration in assays. Biometrika 75: 549--556.
- ↑ Aalen, O. O. 1992. Modelling heterogeneity in survival analysis by the compound Poisson distribution. Ann. Appl. Probab. 2: 951--972.
- ↑ Hougaard, P. , Harvald, B. and Holm, N. V. 1992. Measuring the similarities between the lifetimes of adult Danish twins born between 1881--1930. Journal of the American Statistical Association 87: 17--24.
- ↑ Hougaard, P. 1986. Survival models for heterogeneous populations derived from stable distributions. Biometrika, 73: 387--396.
- ↑ Gilchrist, R. and Drinkwater, D. 1999. Fitting Tweedie models to data with probability of zero responses. Proceedings of the 14th International Workshop on Statistical Modelling, Graz, pp. 207--214.
- ↑ 51.0 51.1 Smyth, G. K. 1996. Regression analysis of quantity data with exact zeros. Proceedings of the Second Australia--Japan Workshop on Stochastic Models in Engineering, Technology and Management. Technology Management Centre, University of Queensland, 572--580.
- ↑ Hasan, M.M.; Dunn, P.K. (2010) "Two Tweedie distributions that are near-optimal for modelling monthly rainfall in Australia", International Journal of Climatology, 21 year-old Glazier James Grippo from Edam, enjoys hang gliding, industrial property developers in singapore developers in singapore and camping. Finds the entire world an motivating place we have spent 4 months at Alejandro de Humboldt National Park.
- ↑ Candy, S. G. 2004. Modelling catch and effort data using generalized linear models, the Tweedie distribution, random vessel effects and random stratum-by-year effects. CCAMLR Science. 11: 59--80.