#PRINCIPAL COMPONENTS ANALYSIS

M=read.table("T8-5.DAT")
M
attach(M)

?prcomp()

PCS = prcomp(M,retx=TRUE,center=TRUE,scale=FALSE)
PCS
PCS$x
PCS$center
PCS$scale.

biplot(PCS,choices=c(1,2),cex=0.5)
biplot(PCS,choices=c(2,3),cex=0.5)
biplot(PCS,choices=c(1,3),cex=0.5)

plot(PCS)

#PCA USING CORRELATION MATRIX

PCS = prcomp(M, scale = TRUE)
PCS
PCS$x
PCS$center
PCS$scale.

biplot(PCS,choices=c(1,2),cex=0.5)

# USING ALTERNATE FUNCTION princomp()
# NOTE DIFFERENCES IN CALCULATION.
# PROTOTYPE BEFORE USING IT!
?princomp