Haven't done much in the field of correlation between different symbols and want to know what tools or services might give me a good primer on how to identify peer companies whose movements another stock is, to some degree, correlated with. FWIW, I'm asking for a specific purpose: I'm looking into pre-market activity and trying to narrow the range of where various stocks will open. When there's high pre-open volume and a narrow bid/ask spread in the minutes leading up to 9:30:00, that's a somewhat reliable signal. But lower-volume stocks often have no pre-market volume and wide pre-open bids/offers that are of little use. So I'm interested in identifying peer companies I can look to for relevant data points. E.g. If I'm tracking a smaller airline like Hawaiin (HA) and trying to get a sense of where it will open after a big industry-disruptive overnight event, even if there's no premarket activity in HA, I might look to major airline stocks UAL, AAL, LUV, DAL, and if they're all -5% to -6% premarket, it's a reasonable assumption HA will open in the same range. So I'm looking for tools that will help me identify peer sets of highly-correlated stocks for me to use to gauge anticipated opens.
Free site and really convenient for use. Also shows rolling vol. http://www.market-topology.com/correlation/