If you want zero if only one variable:
> DF2
sid pid slope
1 1.1 1.1 2
2 1.1 4.1 3
3 1.1 5.1 2
4 2.1 5.1 3
5 3.2 1.2 2
6 3.2 1.7 3
> tapply(DF2$slope, DF2$sid, function(x) if(length(x) == 1) 0 else mean(x))
1.1 2.1 3.2
2.333333 0.000000 2.500000
>
On Fri, Mar 13, 2009 at 6:43 PM, Vedula, Satyanarayana
<sved...@jhsph.edu> wrote:
> Hi,
>
> I was hoping someone could help figure out how to write code for R to do the
> below.
>
> I have data that looks like below. Variables, sid and pid are strings, slope
> is numeric. I need R to get me the mean of slopes for all pid's nested within
> each sid if there are more than one pid's nested within sid.
>
> If there is only pid for a sid, like for 2.1 below, I want R to write a 0.
>
> In the data below, I want to get the mean of slopes for pid (1.1; 4.1; and
> 5.1) because they are nested within sid 1.1 and so on.
>
> Thanks in advance for any suggestions.
> Swaroop
>
> sid pid slope
> 1.1 1.1 2
> 1.1 4.1 3
> 1.1 5.1 2
> 2.1 5.1 3
> 3.2 1.2 2
> 3.2 1.7 3
>
>
>
>
> [[alternative HTML version deleted]]
>
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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.
>
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem that you are trying to solve?
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