very slick Thx.

On Fri, Jul 30, 2010 at 12:44 PM, Wu Gong <wg2f@mtmail.mtsu.edu> wrote:

>
> Hi,
>
> R has a buildin function ?rowsum
>
> rowsum(DF$Data,DF$Id,na.rm=T)
>
> -----
> A R learner.
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