Is it possible that the random forest is somehow adjusting for optimism or
overfitting?
On Apr 1, 2014 7:27 AM, "Schillo, Sonja" <Sonja.Schillo@uni-due.de> wrote:

> Hi all,
>
> I have a question on rpart and randomforest results:
>
> We calculated a single regression tree using rpart and got a pseudo-r2 of
> roundabout 10% (which is not too bad compared to a linear regression on
> this data). Encouraged by this we grew a whole regression forest on the
> same data set using randomforest. But we got  pretty bad pseudo-r2 values
> for the randomforest (even sometimes negative values for some option
> settings).
> We then thought that if we built only one single tree with the
> randomforest routine we should get a result similar to that of rpart. So we
> set the options for randomforest to only one single tree but the resulting
> pseudo-r2 value was negative aswell.
>
> Does anyone have a clue as to why the randomforest results are so bad
> whereas the rpart result is quite ok?
> Is our assumption that a single tree grown by randomforest should give
> similar results as a tree grown by rpart wrong?
> What am I missing here?
>
> Thanks a lot for your help!
> Sonja
>
> ______________________________________________
> R-help@r-project.org 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.
>

	[[alternative HTML version deleted]]


