[datatable-help] aggregate data.table by group by reference

[Matthew Forrest]

Hi all,

A real data.table question here ;-)

I am currently doing this:

output.dt <- input.dt[,lapply(.SD, method.function), by=by.dims]

where method.function is an arbitrary function and by.dims is a list of 
columns (although perhaps I could remove this is the data.table was 
keyed by those columns?)

That doesn't look very data.table-y to me, potentially it would be great 
to do it with := in the proper data.table way.  Is that possible?  I 
have tried a couple of things but haven't managed. The problem is that I 
need to be flexible to deal with arbitrary columns in my data.table.

Any suggestions?

Many thanks,

Matt


-- 
Dr Matthew Forrest
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