`scipy.stats._continuous_distns:invgamma_gen`

source: /scipy/stats/_continuous_distns.py :4902

Signature

   class     invgamma_gen (    momtype    =  1   ,    a    =  None   ,    b    =  None   ,    xtol    =  1e-14   ,    badvalue    =  None   ,    name    =  None   ,    longname    =  None   ,    shapes    =  None   ,    seed    =  None     )

Members

Summary

An inverted gamma continuous random variable.

Extended Summary

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Notes

The probability density function for invgamma is:

f (x, a) = \frac{x ^{- a - 1}}{Γ ( a )} exp (- \frac{1}{x})

for $x >= 0$ , $a > 0$ . $Γ$ is the gamma function (scipy.special.gamma).

invgamma takes a as a shape parameter for $a$ .

invgamma is a special case of gengamma with c=-1, and it is a different parameterization of the scaled inverse chi-squared distribution. Specifically, if the scaled inverse chi-squared distribution is parameterized with degrees of freedom $ν$ and scaling parameter $τ^{2}$ , then it can be modeled using invgamma with a= $ν /2$ and scale= $ν τ^{2} /2$ .

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Aliases

scipy.stats._continuous_distns.invgamma_gen