[datatable-help] Create matrix of columns from grouped rows

[Eric Archer]

Thanks! That's about 2-3x faster. I wasn't familiar with stack/unstack. Now
I have another tool.

Cheers,
e.


----

*Eric Archer, Ph.D.*

Southwest Fisheries Science Center (NMFS/NOAA)
8901 La Jolla Shores Drive
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858-546-7121 (work)
858-546-7003 (FAX)

Marine Mammal Genetics Group: swfsc.noaa.gov/mmtd-mmgenetics
GitHub: github/ericarcher

&

Adjunct Professor, Marine Biology
Scripps Institution of Oceanography
University of California, San Diego
http://profiles.ucsd.edu/frederick.archer


"


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On Wed, Nov 23, 2016 at 11:11 AM, nachti [via R] <
ml-node+s789695n4726778h3 at n4.nabble.com> wrote:

> Try this:
>
> t1 <- dt[, unlist(.SD), by = id]
> t(unstack(t1, form = V1 ~ id))
>
> (I think you get done with the colnames yourself ...)
>
> Cheers,
> ~g
>
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