$1204$ DIMENSION REDUCTION

FIGURE $4\mathrm{.}5$

SCATTER PLOT OF THE SECOND VS$.$ FIRST PRINCIPAL COMPONENTS SCORES FOR THE NORMALIZED BREAKFAST CEREAL OUTPUT

observations can be found. For instance, we see here that children's cereals are close together on the middle$-$left part of the plot.

Using Principal Components for Classification and Prediction

When the goal of the data reduction is to have a smaller set of variables that will serve as predictors, we can proceed as follows: apply PCA to the predictors using the training data. Use the output to determine the number of principal.

Which variables are quantitive$/$ numerical? Which are ordinal? Which are nomial?