This might be a bit of an abuse of the functions, but it seems to work: > dat <- data.frame(A=1, B=2, C=3) > f <- ~ .^3 > colnames(attr(terms(f, data=dat), "factors")) [1] "A" "B" "C" "A:B" "A:C" "B:C" "A:B:C"
Cheers, Andy > From: Alan Simpson > > Hello list > > Does anybody know of any way to create an index of all the possible > combinations of variables (factors) in a data frame? ie for 3 > factors A, B & > C we have > > A > B > C > AB > AC > BC > ABC > > which equates to columns 1, 2, 3, 1:2, (1,3), 2:3 and 1:3. > > I realise that a function like model.matrix does this, but > how to get the > seqence of the index? > > Any help would be greatly appreciated. > > Regards > > Alan Simpson > Roberts Research Group > > > [[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 > > ______________________________________________ [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
