rpart.exp: Initialization function for exponential fitting
Description
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.
Usage
rpart.exp(y, offset, parms, wt)
Arguments
y
the response, which will be of class Surv
offset
optional offset
parms
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
wt
case weights, if present
Value
a list with the necessary initialization components