Bi Plot for PCA

 ## Use datasets:USArrests

data(USArrests) # Get datafile

names(USArrests) # View variable names

## Scaled PCA using entire data.frame

pca1 = prcomp(USArrests, scale = TRUE)

## Both following commands produce same PCA as previous

pca2 = prcomp(~., data = USArrests, scale = TRUE)

pca3 = prcomp(~ Murder + Assault + Rape + UrbanPop,

                data = USArrests, scale = TRUE)

pca1 # View result

names(pca1) # View elements in result object

summary(pca1) # Summary

## Plots for results...

## Scree-plot of variances (Figure 2-5)

#plot(pca1, type = "lines", main = "PCA for USArrests")

## Bi-plot of result (Figure 2-6)

biplot(pca1, col = 1, cex = c(0.8, 1.2), expand = 0.9)