[R] "aggregate" in R

[Sebastián Daza]

plyr is very useful to aggregate data... I strongly recommend it.

On 2/22/2011 5:59 PM, Jeff Newmiller wrote:
> Use ?plyr::ddply
>
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> Hongwei Dong<pdxdong at gmail.com>  wrote:
>
> 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 	[[alternative HTML version deleted]]_____________________________________________
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Sebastián Daza
sebastian.daza at gmail.com