If you look at the map you will notice 11 key areas: Health care, Consumer Cyclicals, Financial Technology, Energy, Capital Goods, Telecom, Utilities, Basic Materials, Transport and Consumer Staples.

Each key area has certain number of core companies. How do I find the correlation between those areas?

[If we have two stocks S and T whose correlation has to be find, then cor(S,T) = sigma (( S(i) - SA) (T(i) - TA)) / (sigmassigmatn)

S(i) & T(i) are closing prices of the stock on the ith day, SA & TA are the mean prices of the stocks, sigmas = standard deviation of S, sigmat = standard deviation of T and n is the number of the days over which the correlation is to be found - Grabbed from a research paper]

Can above info be extended to find the correlation between those 11 key areas? If so, how?

Thank you for your thoughts!