Try:

with(x, sapply(list(mean, var), function(x)tapply(value, ID, x)))

On Thu, Sep 11, 2008 at 2:45 PM, liujb <liujulia7@yahoo.com> 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@r-project.org mailing list
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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