`scipy.stats._continuous_distns:fisk_gen`

source: /scipy/stats/_continuous_distns.py :1360

Signature

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

Members

Summary

A Fisk continuous random variable.

Extended Summary

The Fisk distribution is also known as the log-logistic distribution.

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Notes

The probability density function for fisk is:

f (x, c) = \frac{c x ^{c - 1}}{( 1 + x ^{c} ) ^{2}}

for $x >= 0$ and $c > 0$ .

Please note that the above expression can be transformed into the following one, which is also commonly used:

f (x, c) = \frac{c x ^{- c - 1}}{( 1 + x ^{- c} ) ^{2}}

fisk takes c as a shape parameter for $c$ .

fisk is a special case of burr or burr12 with d=1.

Suppose X is a logistic random variable with location l and scale s. Then Y = exp(X) is a Fisk (log-logistic) random variable with scale = exp(l) and shape c = 1/s.

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Aliases

scipy.stats._continuous_distns.fisk_gen