pdf("C:\\Rmisc\\graphs\\kuehl_06_02.pdf")

aggtype <- c(rep(1:2,each=12))
compmeth <- c(rep(1:4,each=3,times=2))
strength <- c(68,63,65,126,128,133,93,101,98,56,59,57,
              71,66,66,107,110,116,63,60,59,40,41,44)

concrete <- data.frame(aggtype,compmeth,strength)
attach(concrete)

aggtype <- factor(aggtype,levels=1:2,labels=c("B","S"))
compmeth <- factor(compmeth,levels=1:4,labels=c("S","R","L","V"))

tapply(strength,list(aggtype,compmeth),mean)
tapply(strength,list(aggtype,compmeth),sd)

concrete.mod1 <- aov(strength ~ aggtype*compmeth)

anova(concrete.mod1)
summary.lm(concrete.mod1)

library(gmodels)

concrete.mod2 <- lm(strength ~ aggtype:compmeth + 0)

summary(concrete.mod2)

contrasts.mod2 <- rbind(
  'B vs S in Static   ' = c(1,-1,0,0,0,0,0,0),
  'B vs S in Regular  ' = c(0,0,1,-1,0,0,0,0),
  'B vs S in Low      ' = c(0,0,0,0,1,-1,0,0),
  'B vs S in Very Low ' = c(0,0,0,0,0,0,1,-1))

estimable(concrete.mod2,contrasts.mod2)


dev.off()