1.2.13.1.8. statsmodels.api.Poisson.hessian¶
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Poisson.
hessian
(params)[source]¶ Poisson model Hessian matrix of the loglikelihood
Parameters: params : array-like
The parameters of the model
Returns: hess : ndarray, (k_vars, k_vars)
The Hessian, second derivative of loglikelihood function, evaluated at params
Notes
\[\frac{\partial^{2}\ln L}{\partial\beta\partial\beta^{\prime}}=-\sum_{i=1}^{n}\lambda_{i}x_{i}x_{i}^{\prime}\]where the loglinear model is assumed
\[\ln\lambda_{i}=x_{i}\beta\]