Dear all, For treatment contrasts I would :
library(car) data(Prestige) attach(Prestige) levels(type) contrasts(type) <-contr.treatment(levels(type),base =2 ) Alternatively to change my level I would do :- type = relevel(type,ref="prof") Now I want the sigma constraint. For this the LAST level ( the one whose mean is not computed and is equal to -alpha1 - alpha2 (where alpha's are the mean of group i ) is to be set. How do I set that ? Best Regards, Ashim [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.