library(mlbench)
data(Zoo)
help(Zoo)
head(Zoo)
n <- dim(Zoo)[1]
p <- dim(Zoo)[2]-1

X <- as.integer(Zoo[,1]==T)
for (i in 2:p) {
	if (i == 13)	X <- cbind(X,Zoo[,i])
	else X <- cbind(X,as.integer(Zoo[,i]==T))
	}
colnames(X) <-names(Zoo)[1:p]

pc.obj <- princomp(X,cor=T,scores=T)
summary(pc.obj)
pc.obj$loadings

PC.1 <- pc.obj$scores[,1]
PC.2 <- pc.obj$scores[,2]

library(lattice)
type <- levels(Zoo$type)

plot.new()
xyplot(PC.2~PC.1,xlab = "First eigen-axis",ylab = "Second eigen-axis",
	groups=Zoo$type,pch=16,col=1:length(type))

legend(x="topright",legend=type,pch=16,col=1:length(type))