statsmodels.genmod.families.varfuncs.NegativeBinomial¶

class statsmodels.genmod.families.varfuncs.NegativeBinomial(alpha=1.0)[source]¶

Negative binomial variance function

Parameters:¶

alphafloat

The ancillary parameter for the negative binomial variance function. alpha is assumed to be nonstochastic. The default is 1.

Methods

call	Returns the negative binomial variance

Notes

Formulas :

V(mu) = mu + alpha*mu**2

Alias for NegativeBinomial: nbinom = NegativeBinomial()

A private method _clean trims the data by machine epsilon so that p is in (0,inf)

Methods

deriv(mu)

Derivative of the negative binomial variance function.