statsmodels.genmod.families.family.Gamma.loglike_obs

method

Gamma.loglike_obs(endog, mu, var_weights=1.0, scale=1.0)[source]

The log-likelihood function for each observation in terms of the fitted mean response for the Gamma distribution.

Parameters:

endog : array

Usually the endogenous response variable.

mu : array

Usually but not always the fitted mean response variable.

var_weights : array-like

1d array of variance (analytic) weights. The default is 1.

scale : float

The scale parameter. The default is 1.

Returns:

ll_i : float

The value of the loglikelihood evaluated at (endog, mu, var_weights, scale) as defined below.

Notes

\[ll_i = var\_weights_i / scale * (\ln(var\_weights_i * endog_i / (scale * \mu_i)) - (var\_weights_i * endog_i) / (scale * \mu_i)) - \ln \Gamma(var\_weights_i / scale) - \ln(\mu_i)\]