I don't think there is a direct correlation this broad. There are correlation calculators though which may be what you're looking for!
The correlation would imply the sum of both beeing a constant. 2017 has proven that we can soar instead.
We should be looking out for the total size of the 'coinomy. Total sum of alts and bitcoin added together.
If whales dump their alts for dollars, for pumping bitcoin onto a new ATH we are actually loosing total substance in the process. And then, that correlation is observable. And those news about ATH fizzle fast, people calling "Bubble" and stuff.
...right now BTC dropped down below that $5650 starting point from 10/20/17 which is, have to admit, stressfull for me to take. I was looking at futures (biweekly) who had been looking bullish.
Maybe the topshelf alts are worth a look again, ETH, XMR of course, ZEC even? Found a really obscure DAG based alt but their dev team just splitted into halves