Dear Lotta,

Try

my.df <- data.frame(a <- c(1,6,10,11,3,5,10), group <- c(5,5,5,5,9,9,9))
tapply(my.df$a,my.df$group,median)
5 9
8 5

See ?tapply and/or ?aggregate for more information.

HTH,

Jorge




On Fri, Aug 1, 2008 at 1:30 PM, Lotta R <lottajane@gmail.com> wrote:

> Hi all,
>
> I have data that looks like
>
> number|grouping
>
>
> I would like to preform stats for each grouping
>
> so
>
> 1|5
> 6|5
> 10|5
> 11|5
> 3|9
> 5|9
> 10|9
>
> Say I would like to take the median for above, I should be returned 2
> lines,
> one for group #5 and one for group #9
>
> Does this make sense?
>
> I am sorry for the basic question, can someone give me the name of a good
> book as well?
>
> Thanks,
> Lotta
>
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>
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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