Cuckoos1 <- read.table("c:/temp/cuckoos2.dat",header=T)
names(Cuckoos1)

Cuckoos1$Species <- as.factor(Cuckoos1$Species)    # to make sure that Species is a factor, not numeric

boxplot(Length ~ Species, data=Cuckoos1,main="Cuckoo data")

anova(lm(Length ~ Species, data=Cuckoos1))

windows()
par(mfrow=c(2,2))  
plot(lm(Length ~ Species, data=Cuckoos1))
par(mfrow=c(1,1))  


 # these expressions calculate the sum of squares for a contrast ' Pipits vs Robins'

contrast1 <- c(0,1,0,-2,1,0)

l1hat <- contrast1 %*% tapply(Cuckoos1$Length,Cuckoos1$Species,mean)

denoml1hat <- contrast1^2 / tapply(Cuckoos1$Length,Cuckoos1$Species,length)

ssl1hat <- l1hat^2 / sum(denoml1hat)

 # Tukey multiple comparisons

TukeyHSD(aov(Length ~ Species, data=Cuckoos1),"Species" )

plot(TukeyHSD(aov(Length ~ Species, data=Cuckoos1),"Species" ))