Ex. 12.8

Ex. 12.8

Show that coefficients \(\beta_\ell\) found by optimal scoring are proportional to the discriminant directions \(\nu_\ell\) found by linear discriminant analysis.

Soln. 12.8

From Ex. 12.6 we know that the solution of optimal scoring problem (12.52) (with \(\bb{H}\) being identity matrix) is the same (up to coefficient) as ordinary least squares. From Ex. 4.2 we know that the latter is proportional to LDA directions. Therefore, the optimal scoring coefficients are also proportional to LDA directions.

An alternative way is to link optimal scoring and discriminant directions via canonical correlation analysis, see Section 3.4 in \cite{hastie1995penalized} for more details.