<cberry <at> tajo.ucsd.edu> writes: > > Alexandra <alku <at> imm.dtu.dk> writes: > [snip]
Close, but not quite. The problem lies in terms() Here are the attr(terms(...),"factors") matrices: > attributes(terms(Y ~ x:A + A:B,data=dat))$factors x:A A:B Y 0 0 x 2 0 A 2 2 B 0 1 > attributes(terms(Y ~ A:B + x:A ,data=dat))$factors A:B A:x Y 0 0 A 2 2 B 2 0 x 0 1 As you see, the encoding of x and B are treated differently under the two orderings. See ?terms.object for what those codes mean. Same deal for these seemingly equivalent formulae: > attributes(terms(Y ~ (x + A + B)^2-A,data=dat))$factors x B x:A x:B A:B Y 0 0 0 0 0 x 1 0 2 1 0 A 0 0 1 0 1 B 0 1 0 1 1 > attributes(terms(Y ~ (A + B + x)^2-A,data=dat))$factors B x A:B A:x B:x Y 0 0 0 0 0 A 0 0 1 1 0 B 1 0 2 0 1 x 0 1 0 1 1 > (quoting removed to make Gmane happy) AFAICS, this is a bug. I think so too, although I haven't got my head around it yet. Chuck, are you willing to post a summary of this to r-devel for discussion ... and/or post a bug report? ______________________________________________ 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.
