[franklin_p_dyer]

Thanks for the feedback! The business with `cbind` is a facepalm, I'll definitely fix that. I don't think it will affect performance much since that last step won't be repeated many times, but it makes me cringe now knowing how redundant it is.

Good advice on `col_grouping` as well, accessing those components of an aggregation rule by index rather than by name is a bad code smell and decreases readability for sure.

[kuhewa]

Main issue with cbind()ing to matrix then data.frame is conversion of all columns to the same type and potential loss of information