T Mu <muster <at> gmail.com> writes: > > Hi all, > > I am trying to do a ordered probit regression using polr(), replicating a > result from SAS. > > >polr(y ~ x, dat, method='probit') > > suppose the model is y ~ x, where y is a factor with 3 levels and x is a > factor with 5 levels, > > To get coefficients, SAS by default use the last level as reference, R by > default use the first level (correct me if I was wrong),
Yes. > I tried relevel, reorder, contrasts, but no success. I found what really > matters is I am sure those can help but you need to be carefull to "reorder" levels that the order is the same in SAS and R. > >options(contrasts = c("contr.treatment", "contr.poly")) > > or > > >options(contrasts = c("contr.SAS", "contr.poly")) You can also set contrasts directly to factors via contrasts(x) <- contr.SAS where x is your factor. You can also set different contrasts to different factors. Gregor ______________________________________________ R-help@stat.math.ethz.ch 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.