Principle components analysis

data(iris)

# log transform 
log.ir <- log(iris[, 1:4])
ir.species <- iris[, 5]
 
# apply PCA - scale. = TRUE is highly 
# advisable, but default is FALSE. 
ir.pca <- prcomp(log.ir,
                 center = TRUE,
                 scale. = TRUE) 

# plot method
plot(ir.pca, type = "l")

biplot(ir.pca)