[R] Sum over indexed value

[Henrique Dallazuanna]

Try this:

with(DF, rowsum(Col2, Col1))

On Mon, Nov 16, 2009 at 3:49 PM, Gunadi <boydkramer at gmail.com> wrote:
>
> I am sure this is easy but I am not finding a function to do this.
>
> I have two columns in a matrix. The first column contains multiple entries
> of numbers from 1 to 100 (i.e. 10 ones, 8 twos etc.). The second column
> contains unique numbers. I want to sum the numbers in column two based on
> the indexed values in column one (e.g. sum of all values in column two
> associated with the value 1 in column one). I would like two columns in
> return - the indexed value in column one (i.e. this time no duplicates) and
> the sum in column two.
>
> How do I do this?
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-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O