Data <- read.table("C:/Documents and Settings/steeleb/My Documents/Desktop/MiceDiets.txt",header=FALSE)

names(Data) <- c("Lifetime","Diet")
o <- order(Data$Diet)
Data <- Data[o,]

head(Data)

y <- Data[,"Lifetime"]
X <- Data[,"Diet"]
boxplot(y~X,ylab="Lifetime",xlab="Diet")

contrasts(X) <- contr.treatment(length(levels(X)),base=1)
lm.obj <- lm(y~X)
cbind(X,model.matrix(lm.obj))


contrasts(X) <- contr.sum(length(levels(X)),base=1)
lm.obj <- lm(y~X)
cbind(X,model.matrix(lm.obj))


summary(lm.obj)
anova(lm.obj)

lm.obj <- lm(y~X-1)
summary(lm.obj)
anova(lm.obj)