Hi, On Wed, Nov 7, 2012 at 5:03 PM, Alexander Shenkin <ashen...@ufl.edu> wrote: > Hello, > > I'm trying to extract the independent variables from a formula.
This is somewhat ambiguous. Do you want the actual columns of values? The quoted variable names? Including the interaction term or not? If you just want the quoted column names names(as.quoted(a))[-1] will do it. If you want to include the interaction term you can use labels(terms(a)) > closest I've been able to come, aside from rolling my own, is the following: > >> a = y ~ b * x >> attr(terms(formula(a)),"variables") a is already a formula, so you can shorten this to attr(terms(a),"variables") Hope this helps! Ista > > The reason I'm doing this is that I'm building a grid of points that I > use to construct a 3-d model prediction surface in rgl. If there are > more than two independent variables, I need to set the other ones to 0 > in the dataframe for the predict() routine. In order to do that, I need > to know what those variables are. > > I suspect there's a better way to go about doing what I'm doing (perhaps > using the model.* family of functions). But, in the meantime, just > extracting the independent variables will move me forward. > > Thanks, > Allie > > ______________________________________________ > 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. ______________________________________________ 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.
