[R] rpart - the xval argument in rpart.control and in xpred.rpart

[Paolo Radaelli]

Dear R users,
I'm working with the rpart package and want to evaluate the performance of 
user defined split  functions.
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. If I am correct this means that for 
xpred.rpart, xval denots the number V of one V-fold cross validation while 
for rpart.control it denotes the number of times that the cross-validation 
is performed. Am I right ? If so, how many subsets compose the learning 
sample when performing one of the xval cross-validations ? Is it a 10-fold 
cross-validation repeated xval=10 times ?
Thank you for your help

Paolo

Paolo Radaelli
Dipartimento di Metodi Quantitativi per le Scienze Economiche ed Aziendali
Facoltà di Economia
Università degli Studi di Milano-Bicocca
Via Bicocca degli Arcimboldi, 8
20126 Milano
Italy
e-mail paolo.radaelli at unimib.it
Tel +39 02 6448 3163
Fax +39 02 6448 3105