[R] How to use a validation set rather than the default cross-validation in rpart() ?

[Quin Wills]

Many thanks. I'm using it for pruning and was hoping that rpart allows use
of a validation set rather than cross-validation for generating a CP/error
table.

-----Original Message-----
From: Uwe Ligges [mailto:ligges at statistik.uni-dortmund.de] 
Sent: 03 May 2006 07:53
To: Quin Wills
Cc: r-help at stat.math.ethz.ch
Subject: Re: [R] How to use a validation set rather than the default
cross-validation in rpart() ?

Quin Wills wrote:

> I want use a validation set for my classification tree rather than the
> default 10-fold validation in rpart() but can't see which arguments to use
> to get this right. Advice appreciated thanks. I assume that this is
> possible!

You cannot for the internal algorithm that optimizes the splits of the 
tree. Of course you can do so for estimating the misclassification rate 
(or whatever), but this has nothing to do with rpart() itself....

Uwe Ligges