[R] Averaging rows if a condition is true.

[Steve Lianoglou]

Hi,

On Mon, Sep 7, 2009 at 11:46 AM, A Ezhil<ezhil02 at yahoo.com> wrote:
> Dear All,
>
> I have matrix (50000 X 60) of subjects and their responses to a set of questions. All responses are classified into categories (500). I would like to average all subject's responses for each category. I wrote a code using a for loop but is not working. Could please tell me what's wrong with the code? I guess, there is a elegant R way of doing the same thing.

The dlply function in the plyr library provides a very easy and
intuitive way to do this ... if you're having problems using it,
please post a small representative matrix of your data that we can
paste into our own R session to slice and dice for you as an example.

-steve

-- 
Steve Lianoglou
Graduate Student: Computational Systems Biology
 | Memorial Sloan-Kettering Cancer Center
 | Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact