statsmodels.duration.hazard_regression.PHReg.robust_covariance¶
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PHReg.
robust_covariance
(params)[source]¶ Returns a covariance matrix for the proportional hazards model regresion coefficient estimates that is robust to certain forms of model misspecification.
Parameters: params : ndarray
The parameter vector at which the covariance matrix is calculated.
Returns: The robust covariance matrix as a square ndarray.
Notes
This function uses the groups argument to determine groups within which observations may be dependent. The covariance matrix is calculated using the Huber-White “sandwich” approach.