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.
