A Friendly Introduction to Principal Component Analysis

Brilliant!

It is both completely magical and also obvious in retrospect how reducing DNA to its first two principal components yields essentially latitude and longitude.

Also very cool that of course it goes in both directions. With the components computed, you can reconstruct original samples skewed in meaningful ways. Like, you can take an individual person's DNA and see how would it be different if their family had lived 500km to the east.

Title needs (2020)