[R] Rpart, custom penalty for an error
m.blizinski at wit.edu.pl
Sun Sep 10 19:09:42 CEST 2006
Hello all R-help list subscribers,
I'd like to create a regression tree of a data set with binary response
variable. Only 5% of observations are a success, so the regression tree
will not find really any variable value combinations that will yield
more than 50% of probability of success. I am however interested in
areas where the probability of success is noticeably higher than 5%, for
example 20%. I've tried rpart and the weights option, increasing the
weights of the success-observations.
It works as expected in terms of the tree creation: instead of a single
root, a tree is being built. But the tree plot() and text() are somewhat
misleading. I'm interested in the observation counts inside each leaf.
I use the "use.n = TRUE" parameter. The counts displayed are misleading,
the numbers of successes are not the original numbers from the sample,
they seem to be cloned success-observations.
I'd like to split the tree just as weights parameter allows me to,
keeping the original number of observations in the tree plot. Is it
possible? If yes, how?
Maciej Bliziński <m.blizinski at wit.edu.pl>
More information about the R-help