Note that all.vars(terms(fit)) only looks at the formula in the terms object and throws away all the analysis done by rpart's call to terms(formula,data). Here is a contrived example of that approach failing:
> ageThreshold <- 50 > fit3 <- rpart(Kyphosis=="present" ~ (Age>ageThreshold) + log(Number, base=2) + Start, data=kyphosis) > all.vars(terms(fit3)) [1] "Kyphosis" "Age" "ageThreshold" "Number" "Start" Looking at the attributes of the terms object tells you what I think you want: > attr(terms(fit3), "response") # 1=>there is a response variable, 0=>no response [1] 1 > as.list(attr(terms(fit3), "variables"))[-1] [[1]] Kyphosis == "present" [[2]] Age > ageThreshold [[3]] log(Number, base = 2) [[4]] Start rpart doesn't allow interaction terms (x:y), but if it did you would want to look at the "factors" attribute to see which items in the "variables" lists are in each term of the expanded formula. Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Tal Galili > Sent: Wednesday, January 26, 2011 10:07 AM > To: Henrique Dallazuanna > Cc: [email protected] > Subject: Re: [R] Extracting the terms from an rpart object > > Thanks Henrique, exactly what I was looking for. > > > ----------------Contact > Details:------------------------------------------------------- > Contact me: [email protected] | 972-52-7275845 > Read me: www.talgalili.com (Hebrew) | www.biostatistics.co.il > (Hebrew) | > www.r-statistics.com (English) > -------------------------------------------------------------- > -------------------------------- > > > > > On Wed, Jan 26, 2011 at 7:40 PM, Henrique Dallazuanna > <[email protected]>wrote: > > > Try this: > > > > all.vars(terms(fit1)) > > all.vars(terms(fit2)) > > > > > > On Wed, Jan 26, 2011 at 3:33 PM, Tal Galili > <[email protected]> wrote: > > > >> Hello all, > >> > >> I wish to extract the terms from an rpart object. > >> Specifically, I would like to be able to know what is the response > >> variable > >> (so I could do some manipulation on it). > >> But in general, such a method for rpart will also need to > handle a "." > >> case > >> (see fit2) > >> > >> Here are two simple examples: > >> > >> fit1 <- rpart(Kyphosis ~ Age + Number + Start, data=kyphosis) > >> fit1$call > >> fit2 <- rpart(Kyphosis ~ ., data=kyphosis) > >> fit2$call > >> > >> > >> Is there anything "prettier" then using string manipulation? > >> > >> > >> Thanks. > >> > >> > >> > >> > >> > >> ----------------Contact > >> Details:------------------------------------------------------- > >> Contact me: [email protected] | 972-52-7275845 > >> Read me: www.talgalili.com (Hebrew) | > www.biostatistics.co.il (Hebrew) | > >> www.r-statistics.com (English) > >> > >> > -------------------------------------------------------------- > -------------------------------- > >> > >> [[alternative HTML version deleted]] > >> > >> ______________________________________________ > >> [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. > >> > > > > > > > > -- > > Henrique Dallazuanna > > Curitiba-Paraná-Brasil > > 25° 25' 40" S 49° 16' 22" O > > > > [[alternative HTML version deleted]] > > ______________________________________________ [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.
