This function does the initialization step for rpart, when the response is a survival object. It rescales the data so as to have an exponential baseline hazard and then uses Poisson methods. This function would rarely if ever be called directly by a user.
rpart.exp(y, offset, parms, wt)the response, which will be of class Surv
optional offset
parameters controlling the fit.
This is a list with components shrink and method.
The first is the prior for the coefficient of variation of the
predictions. The second is either "deviance"
or "sqrt" and is the measure used for cross-validation.
If values are missing the defaults are used, which are
"deviance" for the method, and a shrinkage of 1.0 for the
deviance method and 0 for the square root.
case weights, if present
a list with the necessary initialization components