Hello All R Gurus I'm a relatively new user to R and I'm having so problems fully grasping the contrasts notion. So any help will be appreciated. Lately I've been playing around with lme and I was looking at the help files of anova.lme where there is this example options(contrasts = c("contr.treatment", "contr.poly")) fm1BW.lme <- lme(weight ~ Time * Diet, BodyWeight, random = ~ Time) fm2BW.lme <- update(fm1BW.lme, weights = varPower()) # Test a specific contrast anova(fm2BW.lme, L = c("Time:Diet2" = 1, "Time:Diet3" = -1)) after running it I get the following result F-test for linear combination(s) Time:Diet2 Time:Diet3 1 -1 numDF denDF F-value p-value 1 1 157 2.862598 0.0926 My question is how can I test for the Time:Diet1 interaction term and compare all three diets. Best regards, Paschal -- View this message in context: http://www.nabble.com/Help-with-contrasts-tp21326943p21326943.html Sent from the R help mailing list archive at Nabble.com.