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How can I extract the R-square from a fit rpart model?

rsq.rpart(fit)

plots the two graphs, but I simply want to extract the R-square value for the full tree.

I assume this is fairly obvious, but numerous searches didn't really lend anything useful. Any help you can provide will be greatly appreciated.

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1 Answer 1

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The advantage of R is that most of the time you can easily access the source code. So in your case, start with

> rsq.rpart

(without parenthesis) to see what the function actually does. The $R^2$ values are obtained as

tmp <- printcp(fit)
rsq.val <- 1-tmp[,c(3,4)]  

where for each row (aka, No. splits) we have the "apparent" and "relative" (wrt. cross-validation) statistics.

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    $\begingroup$ +1, pressed post the same second your answer appeared. I would add that for a full tree rsq.val[nrow(rsq.val),] is probably what OP wants. $\endgroup$
    – mpiktas
    Dec 28, 2010 at 20:34
  • $\begingroup$ @mpiktas Oups... Needless to say, your comment is very appreciated. $\endgroup$
    – chl
    Dec 28, 2010 at 20:39
  • $\begingroup$ Thanks a bunch. I am (obviously) new to R, and never once did I think to look at the function as you first mentioned. I was trying something similar to your answer, but that is perfect! Thx $\endgroup$
    – Btibert3
    Dec 28, 2010 at 20:50

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