Thanks for the replies. I was just thinking that, for a two variable example, doing X<-cbind(x1,x2,x1*x2) lm(y~X) would work. So maybe that's what I'll do. This also allows me to pick and choose which interactions to include.
Cheers Bill On Sun, Dec 5, 2010 at 8:19 PM, William Simpson <william.a.simp...@gmail.com> wrote: > Suppose I have x variables x1, x2, x3 (however in general I don't know > how many x variables there are). I can do > X<-cbind(x1,x2,x3) > lm(y ~ X) > This fits the no-interaction model with b0, b1, b2, b3. > > How can I get lm() to fit the model that includes interactions when I > pass X to lm()? For my example, > lm(y~x1*x2*x3) > I am looking for something along the lines of > lm(y~X ...) > where ... is some extra stuff I need to fill in. > > Thanks for any help. > Bill > ______________________________________________ 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.
