[R] "aggregate" in R

[Jannis]

The documentation of aggregate tells you that your way will not work. Why don't you aggregate/sum the columns separately? I would doubt that what you want to try to achieve in one go is already implemented somewhere....



Jannis
--- Hongwei Dong <pdxdong at gmail.com> schrieb am Di, 22.2.2011:

> Von: Hongwei Dong <pdxdong at gmail.com>
> Betreff: [R] "aggregate" in R
> An: r-help at r-project.org
> Datum: Dienstag, 22. Februar, 2011 22:25 Uhr
> Hi, R users,
> 
> I'm wondering how I can aggregate data in R with different
> functions for
> different columns. For example:
> 
> x<-rep(1:5,3)
> y<-cbind(x,a=1:15,b=21:35)
> y<-data.frame(y)
> 
> I want to aggregate "a" and "b" in y by "x". With "a", I
> want to use
> function "mean"; with "b", I want to use function "sum". I
> tried:
> 
> > aggregate(y,x,mean(y$a),sum(y$b))
> 
> But I got the error:
> 
> Error in match.fun(FUN) :
>   'mean(y$a)' is not a function, character or symbol
> 
> 
> Anyone can tell me how to fix this problem? Thanks.
> 
> Gary
> 
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> 
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