Murray Pung wrote: > Is it possible to add standard error bars to the means on interaction plots?
Not with interaction.plot(), as far as I know. You might consider the effects package by John Fox. For example: with(ToothGrowth, interaction.plot(dose, supp, len)) ToothGrowth$dose <- as.factor(ToothGrowth$dose) TG.lm <- lm(len ~ supp * dose, data = ToothGrowth) library(effects) # loads lattice and grid packages plot(effect("supp:dose", TG.lm)) You also could construct your own plot using the standard errors produced by effect(): sum.df <- data.frame(len = effect("supp:dose", TG.lm)$fit, se = effect("supp:dose", TG.lm)$se, supp = rep(c("OJ", "VC"), 3), dose = rep(c(.5,1,2), each = 2)) library(Hmisc) xYplot(Cbind(len, len - se, len + se) ~ dose | supp, data=sum.df, type="b", ylim=c(0,30)) xYplot(Cbind(len, len - se, len + se) ~ dose, groups=supp, data=sum.df, type="b", ylim=c(0,30)) > Thanks > Murray -- Chuck Cleland, Ph.D. NDRI, Inc. 71 West 23rd Street, 8th floor New York, NY 10010 tel: (212) 845-4495 (Tu, Th) tel: (732) 512-0171 (M, W, F) fax: (917) 438-0894 ______________________________________________ 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.