Returns the deviance of a fitted model object.
an object for which the deviance is desired.
additional optional argument.
This is a generic function which can be used to extract deviances for fitted models. Consult the individual modeling functions for details on how to use this function.
The value of the deviance extracted from the object
Chambers, J. M. and Hastie, T. J. (1992) Statistical Models in S. Wadsworth & Brooks/Cole.