Is this what you want:
> x <- data.frame(Name=c("A","A","C"), Category=c("a","a","b"),
> Quantity=c(1,2,3))
> aggregate(x$Quantity, list(x$Name, x$Category), FUN=sum)
Group.1 Group.2 x
1 A a 3
2 C b 3
>
'by' is "a list of grouping elements, each as long as the variables in
x." Your version was just sending in the names, not the values.
On Thu, Oct 9, 2008 at 1:14 PM, <[EMAIL PROTECTED]> wrote:
> >From what I read this should work. So please help my misunderstanding:
>
>> x <- data.frame(Name=c("A","A","C"), Category=c("a","a","b"),
>> Quantity=c(1,2,3))
>> x
> Name Category Quantity
> 1 A a 1
> 2 A a 2
> 3 C b 3
>
>> aggregate(x, by=as.list(setdiff(names(x),"Quantity")), sum)
> Error in FUN(X[[1L]], ...) : arguments must have same length
>
> The way I understand it is that 'aggegate' should group the rows that are the
> same (in the above 1,2 are the same and 3 stands alone) and the FUN should be
> applied to the ramaining column. I was expecting a data.frame like:
>
> Name Category Quantity
> 1 A a 3
> 2 C b 3
>
> But that is not what I got. Would someone be so kind as pointing out what I
> am doing wrong?
>
> Thank you.
>
> Kevin
>
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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.
>
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem that you are trying to solve?
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