> I have some problems in understanding the meaning of the xval argument in
> the two functions rpart.control and xpred.rpart. In the former it is defined
> as the number of cross-validations while in the latter it is defined as the
> number of cross-validation groups.
It is the same thing. If xval=10 then the data is divided into 10 disjoint
groups. A model is fit with group 1 left out and that model is used to predict
the observations in group 1; then a model is fit with group 2 left out; then
group 3, ...
So 10 groups = 10 fits of the model.
Terry Therneau
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