On Thu, 2 Nov 2006, Brian Sanborn wrote: > Hi R folks, > > I am using R version 2.2.1 for Unix. I am exploring the rpart function, > in particular the rpart.control parameter. I have tried using different > values for xval (0, 1, 10, 20) leaving other parameters constant but I > receive the same tree after each run. Is the10 fold cross-validation > default still running every time? I would expect the trees to change at > least a little when I change the number of folds in the cross-validation > but this is not the case in my tests. Any advice would be greatly > appreciated.
Why do you expect that? 1) The tree returned is not pruned, and the cross-validation affects other information in the rpart object. 2) The cross-validation is used in choosing the cost-complexity parameter cp, that is the degree of pruning to be applied via e.g. printcp or plotcp. I think you need to study the documentation about using rpart, either its technical reports or MASS chapter 9. -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
