Screegit _top_ ★ Essential

The Screegit is proof that you don’t need high-tech electronics to solve everyday problems. It’s an inexpensive, durable, and highly effective tool that turns a tedious chore into a satisfying "click" as the grime disappears.

Raymond B. Cattell, Multivariate Behavioral Research, 1966 — Explains how to use the “elbow” in eigenvalues to choose number of components/factors. screegit