BUG: Fix some cases of groupby(...).transform with dropna=True by rhshadrach · Pull Request #45953 · pandas-dev/pandas (original) (raw)

It didn't yet get sorted out. In fact, I went to improve the docs because of that issue, and found that dropna was not well supported for transforms. Wanted to first improve this before returning to the docs.

I agree matches is better than equal here - and plan to clarify that groupby(...).transform will align when possible.