ContinuumIO/blaze — pull request #666 by mrocklin (2014-09-24 01:13:10+00:00)
Title: [WIP] Non-reducing split-apply-combine

Grouping operations where the application function applied to each group is not necessarily a reduction. This is not widely supported but may be interesting in some backends, notably Python, Pandas, Spark.

This is analogous to pandas'

df.groupby(...).apply(lambda df: new_df)

See discussion on https://github.com/ContinuumIO/blaze/issues/438

I'd also like to hook up the dplyr `transform/mutate` functions to this. I think that'd be a swell API.