Poisson.deviance(endog, mu, freq_weights=1.0, scale=1.0)[source]

Poisson deviance function


endog : array-like

Endogenous response variable

mu : array-like

Fitted mean response variable

freq_weights : array-like

1d array of frequency weights. The default is 1.

scale : float, optional

An optional scale argument. The default is 1.


deviance : float

The deviance function at (endog,mu,freq_weights,scale) as defined below.


If a constant term is included it is defined as

D = 2 * \sum_i (freq\_weights_i * Y_i * \log(Y_i / \mu_i))/ scale