[R] Calculate mean/var by ID

[Adam D. I. Kramer]

aggregate(value,list(ID=ID),mean)
aggregate(value,list(ID=ID),var)

--Adam

On Thu, 11 Sep 2008, liujb wrote:

>
> Hello,
>
> I have a data set that looks like this.
> ID    value
> 111     5
> 111     6
> 111     2
> 178     7
> 178     3
> 138     3
> 138     8
> 138     7
> 138     6
> .
> .
> .
>
> I'd like to calculate the mean and var for each object identified by the ID.
> I can in theory just loop through the whole thing..., but is there a easier
> way/command which let me calculate the mean/var by ID?
>
> Thanks,
> Julia
> -- 
> View this message in context: http://www.nabble.com/Calculate-mean-var-by-ID-tp19440461p19440461.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>