stdin <- read.table("http://www.stat.ufl.edu/~winner/data/std_intensity.dat", header=F,col.names=c("susp_x","peak_y")) attach(stdin); names(stdin) peak_y <- 1000*peak_y susp_xf<- factor(susp_x,levels=c(99.9,125.3,150.2,174.9),ordered=TRUE) tapply(peak_y,susp_xf,mean) tapply(peak_y,susp_xf,sd) stdin.mod1 <- aov(peak_y~susp_xf) summary.lm(stdin.mod1) anova(stdin.mod1) contrasts(susp_xf) <- cbind(c(-.674207,-.219665,.2259286,.6679435), c(.4978482,-.507638,-.492299,.5020885), c(-.218157,.6663716,-.67572,.2275052)) stdin.mod2 <- aov(peak_y~susp_xf) summary.lm(stdin.mod2) anova(stdin.mod2)