The rpart function allows one to give the cross-validation groups explicitly. So if the number of observations was 10, you could use > rpart( y ~ x1 + x2, data=mydata, xval=c(1,1,2,2,3,3,1,3,2,1)) which causes observations 1,2,7, and 10 to be left out of the first xval sample, 3,4, and 9 out of the second, etc. I was going to write "read the manual page for control.rpart", but it seems I forgot to put this feature into the documentation! Terry Therneau
On 12/28/06, Pedro Ramirez <palmar379 at yahoo.es> wrote:
Dear R-list, I am using the rpart/mvpart-package for selecting a right-sized regression tree by 10-fold cross-validation. My question: Is there a possibility to find out for every observation in which of the ten folds it is lying? I want to use the same folds for validating another regression method (moving averages) in order to choose the better one. Thanks a lot, Pedro