“[Price] movements may be concentrated in stocks that have some things in common, but these need not be economic fundamentals.”
"I wondered if it was possible to cluster stocks based on something other than what’s usually used. I started digging around for datasets and after a few weeks I found one that included scores describing strength of “known and hidden relationships” between stocks."
https://medium.com/@gaetanconsulting/unsupervised-machine-learning-for-fun-profit-with-basket-clusters-17a1161e7aa1