[R] summing up colum values for unique IDs when multiple ID's exist in data frame

[Thomas Lumley]

On Tue, 29 May 2007, Seth Falcon wrote:

> "Young Cho" <young.stat at gmail.com> writes:
>
>> I have data.frame's with IDs and multiple columns. B/c some of IDs
>> showed up more than once, I need sum up colum values to creat a new
>> dataframe with unique ids.
>>
>> I hope there are some cheaper ways of doing it...  Because the
>> dataframe is huge, it takes almost an hour to do the task.  Thanks
>> so much in advance!
>
> Does this do what you want in a faster way?
>


rowsum() should probably be faster (but perhaps not much).

   -thomas

Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle