$.$ In Section $12\mathrm{.}2\mathrm{.}3,$ a formula for calculating PVE was given in Equation $12\mathrm{.}10.$ We also saw that the PVE can be obtained using the sdev

output of the prcomp$()$ function.

On the USArrests data, calculate PVE in two ways:

$($a$)$ Using the sdev output of the prcomp$()$ function, as was done in

Section $12\mathrm{.}2\mathrm{.}3.$