Gavin Simpson wrote: > > Grześ wrote: >> I have a standard database - HouseVotes84 >> For example: >> Class V1 V2 V3 V4 V5 V6 V7 V8 V9 V10 V11 V12 V13 V14 V15 V16 >> 1 republican n y n y y y n n n y <NA> y y y n y >> 2 republican n y n y y y n n n n n y y y n <NA> >> 3 democrat <NA> y y <NA> y y n n n n y n y y n n >> . >> . >> . >> end I build a tree like this: >>> hv.tree1=rpart(Class~.,HouseVotes84) >> everything is ok! My question is: >> What exactly mean "Class~.,"? > > It means include all remaining variables in HouseVotes84 on the rhs of > the formula, i.e. as variables that should be used to predict the Class > variable. > >> >> Why when I use "Class~.," - then I get the best solution but when I use >> as a >> parameter like this: >>> hv.tree2=rpart(V2~.,HouseVotes84) > > Why does this surprise you? You are now trying to predict the variable > V2 (y/n) from Class and all remaining variables. > >> I also get solution but not such good like before. > > They are solutions to two different problems. > > If you want to predict Class, then you need > > Class ~ ., data = HouseVotes84 > > or, to specify exactly which variables to use as predictors of Class, > state them explicitly: > > Class ~ V1 + V3 + V4, data = HouseVotes84 > > I think you should look at the documentation that comes with R (An > Introduction to R) or some of the contributed help documents on the R > Website to read up on model formulae and how to represent models using > this notation. > > HTH > > G > > ______________________________________________ > 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. > >
Thank you very much! -- View this message in context: http://www.nabble.com/Question-about-rpart%28sth%7E.%2Cdatabase%29-tp23117162p23128038.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.
