[R] conditional sum two dataframes

Bert Gunter gunter.berton at gene.com
Thu Jul 26 23:49:30 CEST 2012

The values need not be a data frame as the number of unique months
could be different among the columns, right?. So you're going to have
to rethink your data structure. Probably as a list.

Once you get that straight,?tapply and friends should make it trivial,
if I understand you correctly.

-- Bert

On Thu, Jul 26, 2012 at 10:49 AM, jcrosbie <james at crosb.ie> wrote:
> I have two data frames. One with a matrix of months and the other with a
> matrix of values. The two dataframes correspond to each other. I would like
> to sum up all the values in by month.
> What would be an efficient way to do this?
> a=C(2,3,5,2,3,5)
> b=c(2,6,3,2,6,3)
> c=c(2,6,7,2,6,5)
> months <- data.frame(a,b,c)
> a=C(200,345,5435,27456,3343,555)
> b=c(288,699,377,234,6354,33454)
> c=c(2345,6345,79678,245,676,5089)
> values <- data.frame(a,b,c)
> --
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Bert Gunter
Genentech Nonclinical Biostatistics

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