Hi:

Here's another way:

c1<-c(1,2,3,2,2,3,1,2,2,2)
c2<-c(5,6,7,7,5,7,5,7,6,6)
c3<-rnorm(10)
x <- data.frame(c1 = factor(c1), c2 = factor(c2), c3)
x <- transform(x, mean = ave(c3, c1, c2, FUN = mean))

Yet another with function ddply() in package plyr:
ddply(x, .(c1, c2), transform, mean = mean(c3))

HTH,
Dennis


On Fri, Feb 25, 2011 at 7:14 AM, zem <zmanolova@gmail.com> wrote:

>
> Yeah, you are right
> i want to post an short example what i want to do .. and in the meantime i
> solved the problem ...
> but here is:
> i have something like this dataframe:
> c1<-c(1,2,3,2,2,3,1,2,2,2)
> c2<-c(5,6,7,7,5,7,5,7,6,6)
> c3<-rnorm(10)
> x<-cbind(c1,c2,c3)
> > x
>      c1 c2          c3
>  [1,]  1  5  0.08279036
>  [2,]  2  6  0.59135988
>  [3,]  3  7  1.45520468
>  [4,]  2  7 -1.70094640
>  [5,]  2  5  0.13065228
>  [6,]  3  7 -1.12080980
>  [7,]  1  5  0.42779354
>  [8,]  2  7 -1.53111972
>  [9,]  2  6  0.29299987
> [10,]  2  6 -0.01602095
>
> #whith aggregate i receive this:
> >aggregate(x[,3],list(x[,1],x[,2]),mean)
>  Group.1 Group.2          x
> 1       1       5  0.2552920
> 2       2       5  0.1306523
> 3       2       6  0.2894463
> 4       2       7 -1.6160331
> 5       3       7  0.1671974
>
>
> and the problem was that i was grouping by 2 columns, so i couldn't copy
> the
> result to x.
>
> the solution was i made another column with paste(x[,1],x[,2],sep="_")
> and then i used the solution from this link:
> http://tolstoy.newcastle.edu.au/R/help/06/07/30184.html
> so i solved my problem
>
> Ivan, many thanks for your support and quik responses! :)
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/group-by-in-data-frame-tp3324240p3324608.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
> and provide commented, minimal, self-contained, reproducible code.
>

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