IPE: Incrementally compute linear regression

[mpickering]

trafficstars

At the moment the linear regression is computed by collecting all the samples, and then calling linearRegressionRSqr. OTOH, the mean and stddev are computed incrementally.

Linear regression can also be computed incrementally using the approach outlined in this paper - https://dbs.ifi.uni-heidelberg.de/files/Team/eschubert/publications/SSDBM18-covariance-authorcopy.pdf