Continuous probability distribution
TheKaniadakis Weibull distribution (orκ -Weibull distribution) is aprobability distribution arising as a generalization of theWeibull distribution .[ 1] [ 2] It is one example of aKaniadakisκ -distribution . The κ-Weibull distribution has been adopted successfully for describing a wide variety ofcomplex systems in seismology, economy, epidemiology, among many others.
Probability density function [ edit ] The Kaniadakisκ -Weibull distribution is exhibits power-law right tails, and it has the followingprobability density function :[ 3]
f κ ( x ) = α β x α − 1 1 + κ 2 β 2 x 2 α exp κ ( − β x α ) {\displaystyle f_{_{\kappa }}(x)={\frac {\alpha \beta x^{\alpha -1}}{\sqrt {1+\kappa ^{2}\beta ^{2}x^{2\alpha }}}}\exp _{\kappa }(-\beta x^{\alpha })} valid forx ≥ 0 {\displaystyle x\geq 0} , where| κ | < 1 {\displaystyle |\kappa |<1} is the entropic index associated with theKaniadakis entropy ,β > 0 {\displaystyle \beta >0} is the scale parameter, andα > 0 {\displaystyle \alpha >0} is the shape parameter orWeibull modulus .
TheWeibull distribution is recovered asκ → 0. {\displaystyle \kappa \rightarrow 0.}
Cumulative distribution function [ edit ] Thecumulative distribution function ofκ -Weibull distribution is given by
F κ ( x ) = 1 − exp κ ( − β x α ) {\displaystyle F_{\kappa }(x)=1-\exp _{\kappa }(-\beta x^{\alpha })}
valid forx ≥ 0 {\displaystyle x\geq 0} . The cumulativeWeibull distribution is recovered in the classical limitκ → 0 {\displaystyle \kappa \rightarrow 0} .
Survival distribution and hazard functions [ edit ] The survival distribution function ofκ -Weibull distribution is given by
S κ ( x ) = exp κ ( − β x α ) {\displaystyle S_{\kappa }(x)=\exp _{\kappa }(-\beta x^{\alpha })} valid forx ≥ 0 {\displaystyle x\geq 0} . The survivalWeibull distribution is recovered in the classical limitκ → 0 {\displaystyle \kappa \rightarrow 0} .
Comparison between the Kaniadakis κ-Weibull probability function and its cumulative. The hazard function of theκ -Weibull distribution is obtained through the solution of theκ -rate equation:
S κ ( x ) d x = − h κ S κ ( x ) {\displaystyle {\frac {S_{\kappa }(x)}{dx}}=-h_{\kappa }S_{\kappa }(x)}
withS κ ( 0 ) = 1 {\displaystyle S_{\kappa }(0)=1} , whereh κ {\displaystyle h_{\kappa }} is the hazard function:
h κ = α β x α − 1 1 + κ 2 β 2 x 2 α {\displaystyle h_{\kappa }={\frac {\alpha \beta x^{\alpha -1}}{\sqrt {1+\kappa ^{2}\beta ^{2}x^{2\alpha }}}}} The cumulativeκ -Weibull distribution is related to theκ -hazard function by the following expression:
S κ = e − H κ ( x ) {\displaystyle S_{\kappa }=e^{-H_{\kappa }(x)}} where
H κ ( x ) = ∫ 0 x h κ ( z ) d z {\displaystyle H_{\kappa }(x)=\int _{0}^{x}h_{\kappa }(z)dz} H κ ( x ) = 1 κ arcsinh ( κ β x α ) {\displaystyle H_{\kappa }(x)={\frac {1}{\kappa }}{\textrm {arcsinh}}\left(\kappa \beta x^{\alpha }\right)} is the cumulativeκ -hazard function. The cumulative hazard function of theWeibull distribution is recovered in the classical limitκ → 0 {\displaystyle \kappa \rightarrow 0} :H ( x ) = β x α {\displaystyle H(x)=\beta x^{\alpha }} .
Moments, median and mode[ edit ] Theκ -Weibull distribution has moment of orderm ∈ N {\displaystyle m\in \mathbb {N} } given by
E [ X m ] = | 2 κ β | − m / α 1 + κ m α Γ ( 1 2 κ − m 2 α ) Γ ( 1 2 κ + m 2 α ) Γ ( 1 + m α ) {\displaystyle \operatorname {E} [X^{m}]={\frac {|2\kappa \beta |^{-m/\alpha }}{1+\kappa {\frac {m}{\alpha }}}}{\frac {\Gamma {\Big (}{\frac {1}{2\kappa }}-{\frac {m}{2\alpha }}{\Big )}}{\Gamma {\Big (}{\frac {1}{2\kappa }}+{\frac {m}{2\alpha }}{\Big )}}}\Gamma {\Big (}1+{\frac {m}{\alpha }}{\Big )}} The median and the mode are:
x median ( F κ ) = β − 1 / α ( ln κ ( 2 ) ) 1 / α {\displaystyle x_{\textrm {median}}(F_{\kappa })=\beta ^{-1/\alpha }{\Bigg (}\ln _{\kappa }(2){\Bigg )}^{1/\alpha }} x mode = β − 1 / α ( α 2 + 2 κ 2 ( α − 1 ) 2 κ 2 ( α 2 − κ 2 ) ) 1 / 2 α ( 1 + 4 κ 2 ( α 2 − κ 2 ) ( α − 1 ) 2 [ α 2 + 2 κ 2 ( α − 1 ) ] 2 − 1 ) 1 / 2 α ( α > 1 ) {\displaystyle x_{\textrm {mode}}=\beta ^{-1/\alpha }{\Bigg (}{\frac {\alpha ^{2}+2\kappa ^{2}(\alpha -1)}{2\kappa ^{2}(\alpha ^{2}-\kappa ^{2})}}{\Bigg )}^{1/2\alpha }{\Bigg (}{\sqrt {1+{\frac {4\kappa ^{2}(\alpha ^{2}-\kappa ^{2})(\alpha -1)^{2}}{[\alpha ^{2}+2\kappa ^{2}(\alpha -1)]^{2}}}}}-1{\Bigg )}^{1/2\alpha }\quad (\alpha >1)} Thequantiles are given by the following expression
x quantile ( F κ ) = β − 1 / α [ ln κ ( 1 1 − F κ ) ] 1 / α {\displaystyle x_{\textrm {quantile}}(F_{\kappa })=\beta ^{-1/\alpha }{\Bigg [}\ln _{\kappa }{\Bigg (}{\frac {1}{1-F_{\kappa }}}{\Bigg )}{\Bigg ]}^{1/\alpha }}
with0 ≤ F κ ≤ 1 {\displaystyle 0\leq F_{\kappa }\leq 1} .
TheGini coefficient is:[ 3]
G κ = 1 − α + κ α + 1 2 κ Γ ( 1 κ − 1 2 α ) Γ ( 1 κ + 1 2 α ) Γ ( 1 2 κ + 1 2 α ) Γ ( 1 2 κ − 1 2 α ) {\displaystyle \operatorname {G} _{\kappa }=1-{\frac {\alpha +\kappa }{\alpha +{\frac {1}{2}}\kappa }}{\frac {\Gamma {\Big (}{\frac {1}{\kappa }}-{\frac {1}{2\alpha }}{\Big )}}{\Gamma {\Big (}{\frac {1}{\kappa }}+{\frac {1}{2\alpha }}{\Big )}}}{\frac {\Gamma {\Big (}{\frac {1}{2\kappa }}+{\frac {1}{2\alpha }}{\Big )}}{\Gamma {\Big (}{\frac {1}{2\kappa }}-{\frac {1}{2\alpha }}{\Big )}}}}
Asymptotic behavior [ edit ] Theκ -Weibull distribution II behaves asymptotically as follows:[ 3]
lim x → + ∞ f κ ( x ) ∼ α κ ( 2 κ β ) − 1 / κ x − 1 − α / κ {\displaystyle \lim _{x\to +\infty }f_{\kappa }(x)\sim {\frac {\alpha }{\kappa }}(2\kappa \beta )^{-1/\kappa }x^{-1-\alpha /\kappa }} lim x → 0 + f κ ( x ) = α β x α − 1 {\displaystyle \lim _{x\to 0^{+}}f_{\kappa }(x)=\alpha \beta x^{\alpha -1}} Related distributions [ edit ] Theκ -Weibull distribution has been applied in several areas, such as:
Ineconomy , for analyzingpersonal income models , in order to accurately describing simultaneously the income distribution among the richest part and the great majority of the population.[ 1] [ 4] [ 5] Inseismology , the κ-Weibull represents the statistical distribution of magnitude of the earthquakes distributed across the Earth, generalizing theGutenberg–Richter law ,[ 6] and the interval distributions of seismic data, modeling extreme-event return intervals.[ 7] [ 8] Inepidemiology , the κ-Weibull distribution presents a universal feature for epidemiological analysis.[ 9] ^a b Clementi, F.; Gallegati, M.; Kaniadakis, G. (2007)."κ-generalized statistics in personal income distribution" .The European Physical Journal B .57 (2):187– 193.arXiv :physics/0607293 .Bibcode :2007EPJB...57..187C .doi :10.1140/epjb/e2007-00120-9 .ISSN 1434-6028 .S2CID 15777288 . ^ Clementi, F.;Di Matteo, T. ; Gallegati, M.; Kaniadakis, G. (2008)."The -generalized distribution: A new descriptive model for the size distribution of incomes" .Physica A: Statistical Mechanics and Its Applications .387 (13):3201– 3208.arXiv :0710.3645 .doi :10.1016/j.physa.2008.01.109 .S2CID 2590064 . ^a b c Kaniadakis, G. (2021-01-01)."New power-law tailed distributions emerging in κ-statistics (a)" .Europhysics Letters .133 (1) 10002.arXiv :2203.01743 .Bibcode :2021EL....13310002K .doi :10.1209/0295-5075/133/10002 .ISSN 0295-5075 .S2CID 234144356 . ^ Clementi, Fabio; Gallegati, Mauro; Kaniadakis, Giorgio (October 2010)."A model of personal income distribution with application to Italian data" .Empirical Economics .39 (2):559– 591.doi :10.1007/s00181-009-0318-2 .ISSN 0377-7332 .S2CID 154273794 . ^ Clementi, F; Gallegati, M; Kaniadakis, G (2012-12-06)."A generalized statistical model for the size distribution of wealth" .Journal of Statistical Mechanics: Theory and Experiment .2012 (12) P12006.arXiv :1209.4787 .Bibcode :2012JSMTE..12..006C .doi :10.1088/1742-5468/2012/12/P12006 .ISSN 1742-5468 .S2CID 18961951 . ^ da Silva, Sérgio Luiz E.F. (2021)."κ -generalised Gutenberg–Richter law and the self-similarity of earthquakes" .Chaos, Solitons & Fractals .143 110622.Bibcode :2021CSF...14310622D .doi :10.1016/j.chaos.2020.110622 .S2CID 234063959 . ^ Hristopulos, Dionissios T.; Petrakis, Manolis P.; Kaniadakis, Giorgio (2014-05-28)."Finite-size effects on return interval distributions for weakest-link-scaling systems" .Physical Review E .89 (5) 052142.arXiv :1308.1881 .Bibcode :2014PhRvE..89e2142H .doi :10.1103/PhysRevE.89.052142 .ISSN 1539-3755 .PMID 25353774 .S2CID 22310350 . ^ Hristopulos, Dionissios; Petrakis, Manolis; Kaniadakis, Giorgio (2015-03-09)."Weakest-Link Scaling and Extreme Events in Finite-Sized Systems" .Entropy .17 (3):1103– 1122.Bibcode :2015Entrp..17.1103H .doi :10.3390/e17031103 .ISSN 1099-4300 . ^ Kaniadakis, Giorgio; Baldi, Mauro M.; Deisboeck, Thomas S.; Grisolia, Giulia; Hristopulos, Dionissios T.; Scarfone, Antonio M.; Sparavigna, Amelia; Wada, Tatsuaki; Lucia, Umberto (2020)."The κ-statistics approach to epidemiology" .Scientific Reports .10 (1): 19949.Bibcode :2020NatSR..1019949K .doi :10.1038/s41598-020-76673-3 .ISSN 2045-2322 .PMC 7673996 .PMID 33203913 .