Long gone are the days where it's a simple "BTC UP, ALTS DOWN" and vice versa.
In fact, I would say that it now resembles more of a general "BTC UP, ALTS UP" and vice versa, though it's not as simple as that, with many small waves within waves, each with its own unique characteristics.
However, in the grand scheme of things, you can probably tell that both go up in tandem in the largest trend. Also, there is some pattern we can glean from this, but you really need to delve deeper into the price action comparison between BTC & ALTs since beginning of 2017 to get a clearer picture of the characteristics of the "waves within waves".