[R] aggregating variables (sum within groups)

[Ivan Calandra]

Hi David,

You have your answer in the question:
aggregate()

aggregate(cbind(var1,var2)~group, data=testdata, FUN=sum)

Although I am not sure what you intended to do with "testdata$x<-" as 
the result cannot have the same number of rows than testdata


HTH,
Ivan

--
Ivan Calandra, ATER
University of Reims Champagne-Ardenne
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Le 26/02/15 13:02, David Studer a écrit :
> Hello everybody!
>
> I have a (probabely very easy) problem. Even though I was looking in
> several r-books
> I could not find a suitable function to this problem, that's why I hope
> that someone here
> could help me:
>
> # Sample data:
> group<-c("A","A","A","B","B","C","C","C")
> var1<-c(1,0,0,1,1,0,NA,1)
> var2<-c(0,1,NA,0,1,1,0,0)
> testdata<-data.frame(group, var1, var2)
>
> Now, I'd like to generate two aggregated variables:
>
> testdata$x<- ???   should count the sum of var1 within each group (=4)
> testdata$y<- ???   should count the sum of var2 within each group (=3)
>
> Therefore I am looking for a function like ave() which does not calculate
> the mean value but a sum.
>
> Thank you for any hints!
>
> David
>
> 	[[alternative HTML version deleted]]
>
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