## R-Script to Exercise 3

## Task 2

##Read in the data.

drill <- read.table(file="http://stat.ethz.ch/Teaching/Datasets/drill.txt",header=TRUE)
                       
str(drill)

drill$A <- as.factor(drill$A)
drill$B <- as.factor(drill$B)
drill$C <- as.factor(drill$C)
drill$D <- as.factor(drill$D)

## a)

par(mfrow=c(2,2))
plot(drill$A,drill$Y,xlab="A")
plot(drill$B,drill$Y,xlab="B")
plot(drill$C,drill$Y,xlab="C")
plot(drill$D,drill$Y,xlab="D")

par(mfrow=c(2,3))
interaction.plot(drill$B,drill$C,drill$Y)
interaction.plot(drill$C,drill$B,drill$Y)
interaction.plot(drill$B,drill$D,drill$Y)
interaction.plot(drill$D,drill$B,drill$Y)
interaction.plot(drill$C,drill$D,drill$Y)
interaction.plot(drill$D,drill$C,drill$Y)

## b)

mod1 <- aov(Y~A*B*C*D,data=drill)
summary(mod1)

## c)

mod2 <- aov(Y~A+B+C+D+A:B+A:C+A:D+B:C+B:D+C:D,data=drill)
summary(mod2)

## d)

par(mfrow=c(2,2))
plot(mod2)

library(faraway)

halfnorm(mod2$effects[-1],labs=names(mod2$effects[-1]))

drill.e <- drill
drill.e$Y <- log(drill$Y)

mod3 <- aov(Y~A+B+C+D+A:B+A:C+A:D+B:C+B:D+C:D,data=drill.e)
summary(mod3)

par(mfrow=c(2,2))
plot(mod3)


## Task 3

## ## Read in the data.


soft <- read.table(file="http://stat.ethz.ch/Teaching/Datasets/softdrinkANOVA.txt",header=TRUE)
                         
soft$sugar <- as.factor(soft$sugar)
soft$soda <- as.factor(soft$soda)
soft$water <- as.factor(soft$water)
soft$temp <- as.factor(soft$temp)

## a)

par(mfrow=c(2,2))
plot(soft$sugar,soft$score,sub="sugar")
plot(soft$soda,soft$score,sub="soda")
plot(soft$water,soft$score,sub="water")
plot(soft$temp,soft$score,sub="temp")


## b)

modS <- aov(score~sugar*soda*water*temp,data=soft)
summary(modS)


par(mfrow=c(2,2))
plot(modS)

library(faraway)

halfnorm(modS$effects[-1],labs=names(modS$effects[-1]))