Regarding my earlier tweet about eigenvectors, some of you have asked for more explanation about page rank. Here’s a chapter from “The Joy of x“ where I tried to do that. 1/5 
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Coda: The equations on page 197, which say “importance before” equals “importance after”, can be written as a matrix equation Ax=x, where x = (x,y,z) encodes the importance or page rank of each page. The point: Ax=x says x is an eigenvector with eigenvalue equal to 1.
Caveat: Experts will realize I’ve left out a lot about page rank. This was just meant to give you a taste. For some of the missing details, start with Wikipedia en.m.wikipedia.org/wiki/PageRank or search for more authoritative pages on the Internet... probably using page rank!
