[R] help

[Christine Tuleau]

Hello,

I am a new member, and I need your help.
For my work (thesis), I use the package rpart to construct trees.
But, to continu my studies, I need to calcule the 'variable importance'. But, I 
don't find a program to do this in the implementation of R.
Is there someone who know if there exist a program which calculate the 'variable 
importance', notion defined by Breiman and al. in CART ?
If this program exists, could you tell me where I can find it, to use it?

Thanks a lot, and sorry for my english.

Christine Tuleau