statsmodels.tools.eval_measures.
aic
Akaike information criterion
llf : float
value of the loglikelihood
nobs : int
number of observations
df_modelwc : int
number of parameters including constant
aic : float
information criterion
References
http://en.wikipedia.org/wiki/Akaike_information_criterion
statsmodels.tools.numdiff.approx_hess_cs
statsmodels.tools.eval_measures.aic_sigma