The current GeneralizedLinearRegression model does not support offset. The offset can be useful to take into account exposure, or for testing incremental effect of new variables. It is possible to use weights in current environment to achieve the same effect of specifying offset for certain models, e.g., Poisson & Binomial with log offset, it is desirable to have the offset option to work with more general cases, e.g., negative offset or offset that is hard to specify using weights (e.g., offset to the probability rather than odds in logistic regression).
Effort would involve:
- update regression class to support offsetCol
- update IWLS to take into account of offset
- add test case for offset
I can start working on this if the community approves this feature.