[R] Conditional Row Sum

[Gabor Grothendieck]

Using the built in data.frame iris sum each of the first 4 columns for
each value of the 5th column.

rowsum(iris[,-5], iris[,5])


On 4/20/06, Sachin J <sachinj.2006 at yahoo.com> wrote:
> Hi,
>
>  How can I accomplish this in R. Example:
>
>  R1  R2
>  3     101
>  4     102
>  3     102
>  18    102
>  11    101
>
>  I want to find Sum(101) =  14 - i.e SUM(R1) where R2 = 101
>                  Sum(102) = 25    - SUM(R2) where R2 = 102
>
>  TIA
>  Sachin
>
>
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>
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