[R] Newbie question about "grouping"

[hadley wickham]

On Wed, Jan 28, 2009 at 8:13 AM, Rixon, John C. <JCRixon at wellington.com> wrote:
> Hi folks:
>
> I am a SQL guy who just downloaded and installed R yesterday.  I am
> trying to evaluate some "complex" aggregations we are currently
> performing with Syncsort (and have tried in Oracle) with R.  I have
> loaded data in a dataframe and have performed some of the simple
> aggregations on a subset of data.  What I do not see how to do though,
> is to "group" the aggregations on a particular key value (e.g., sum
> market_value over account_id).
>
> If you can point me in the right direction I'd very much appreciate it.

Have a look at the plyr package, http://had.co.nz/plyr, and associated
documentation. If you're doing pivot table type aggregations, you
might also want to have a look at the reshape package,
http://had.co.nz/reshape.


Hadley

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