?contrasts ?C Cheers, Bert
On Wed, Oct 23, 2013 at 6:00 AM, Rafael Moral <rafa_moral2...@yahoo.com.br> wrote: > Dear useRs, > I was wondering if there was a way of changing the model matrix restriction > automatically in the formula statement when fitting a model using, for > example, lm(). > When we do > > set.seed(100) > y <- rnorm(12) > A <- gl(3, 4) > summary(lm(y ~ A)) > > we obtain A1=0 as a baseline and A2 and A3 as effects. > However, if I want to use A2=0 as a baseline, I can do > > X <- cbind(1, model.matrix(lm(y ~ A - 1)))[,-3] > summary(lm(y ~ X)) > > I wonder if there is a way of specifying the restriction in the parameters > directly in the formula argument instead of building the desired model matrix. > > Best wishes, > Rafael. > > ______________________________________________ > 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. -- Bert Gunter Genentech Nonclinical Biostatistics (650) 467-7374 ______________________________________________ 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.
