Adam Klein

I couldn't help but tinker a bit - this yields a 15x speed improvement, but doesn't handle multiple columns in either the aggregate-by or group-by parameters - but it does...

And, this gets us down another 3x... I wonder if any of this can be generalized without losing speed. ``` member frame.FoldColumnBy(groupBy:_, aggBy:_, init:_, foldl:Func) = let dct = Dictionary()...

Great idea!

Yeah, the `join` function could be as simple as unpacking the `Series` into a `Frame`.

I think the first idea is easier to implement, and would be useful in general.

Nobody seems to like the "funny type-specific function" approach. Is there another way? What about a type hint function? Eg, ``` let indexRows (t:'R2 -> 'R2) column (frame:Frame) : Frame(column)...

I upvoted your F# fix proposal :)

Or at least document this, that should be sufficient.

Aha, I see ... I think it actually tries to convert the _column_ to type integer, rather than the fill value to the type of the column. I think the...

(sample is linqpad script, hence Dump() call)