Thanks. Not what I was hoping to hear, but it's good to know. Back to the drawing board(: Perhaps since I really don't want to allow interactions and other exotica, I should just have the names of the covariates passed in, and then construct the formula from that (with paste and as.formula?).
A couple of follow up questions. On Fri, 2003-09-12 at 16:12, Thomas Lumley wrote: > On Fri, 12 Sep 2003, Ross Boylan wrote: ..... > > > b) How can I get the response variable out of the "variables" > > attribute? In my example, > > response is 1, but attr(t, "variables")[1] is list(). > > Possible answer: attr(t, "variables")[[response+1]] looks right, > > and is of class name. Hence the interest in question 2. > Is attr(t, "variables")[[response+1]] always the right term, though it may not be of class name if the response is an expression? > The "factors" attribute has row names corresponding to variables and > column names corresponding to terms. > Is the first row name always the response (though it may not be a simple variable name)? .... > > An example of the sort of thing you're trying to do is in > untangle.specials() in the survival package, which is used to locate terms > and variables for strata() and cluster() in coxph(). It uses the dimnames > of the "factors" attribute as keys. > I'm working on a modified version of those routines, so I'll have another look. The strata term was one of the reasons I was mucking around. By the way, do you or anyone know what's special about specials? The only thing the documentation mentioned (that I saw) was that terms that were special were flagged as such. > -thomas > > Thomas Lumley Assoc. Professor, Biostatistics > [EMAIL PROTECTED] University of Washington, Seattle ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
