[R] aggregating variables (sum within groups)

[Brandstätter Christian]

Dear David,

your email is quite confusing. Do you want to get the sum for each group
(A,B,C) or each variable as would be indicated by your result?


sum by group:
aggregate(data=testdata,var1~group,sum)

count by group:
aggregate(data=testdata,var1~group,length)

sum by variable:
sum(na.omit(testdata$var1))

But homework shouldn't be posted on this list.
Best regards
Christian



2015-02-26 13:02 GMT+01:00 David Studer <studerov at gmail.com>:

> 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
>
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>
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