[R] Combining data

[David Winsemius]

On Nov 17, 2011, at 10:37 AM, Nasrin Pak wrote:

> Hi all;
>
> It seemed to be easy at first, but I didn't manage to find the answer
> through the google search. I have a set of data for every second of  
> the
> experiment, but I don't need such a high resolution for my analysis.  
> I want
> to replace every 30 row of my data with their average value. And  
> then save
> the new data set in a new csv file to be able to have a smaller  
> excel data
> sheet. What is the command for combining certain number of data into  
> their
> average value?
>

This aggregates mean values in groups of ten.

 > aggregate(data.frame(a=rnorm(100)), list(rep(1:10, each=10)),  
FUN=mean)
    Group.1           a
1        1 -0.59492893
2        2  0.20087525
3        3 -0.06310919
4        4 -0.60778424
5        5 -0.01435818
6        6 -0.01159243
7        7  0.05921309
8        8 -0.04881492
9        9  0.43796040
10      10 -0.02968688

> Thank you
>
> -- 
> Nasrin  Pak
> MSc Student in Environmental Physics
> University of Calgary
>
> 	[[alternative HTML version deleted]]
>
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David Winsemius, MD
West Hartford, CT