dep.lib <- read.csv( "http://www.stat.ufl.edu/~winner/data/depressant_libido.csv") attach(dep.lib); names(dep.lib) drug <- factor(drug, levels=1:4, labels=c("Prozac","Paxil","Zoloft","Wellbutrin")) ## Intercept = mu1 dl.mod1 <- aov(libido ~ drug) summary.lm(dl.mod1) options(contrasts=c("contr.sum","contr.poly")) ## sum(alpha) = 0 dl.mod2 <- aov(libido ~ drug) summary.lm(dl.mod2) ## cell means model dl.mod3 <- lm(libido ~ drug - 1) summary(dl.mod3)