[R] apply function across dataframe columns for non-exclusive groups

[Jeff Newmiller]

The calculation appears to be sum(a)/(sum(a)+sum(b)).

library(dplyr)
library(tidyr)
result <- (   this_df
          %>% gather( group, truth, -c(a,b) )
          %>% group_by( group, truth )
          %>% summarise( calc = sum(a)/(sum(a)+sum(b)) )
          %>% as.data.frame
          )

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Sent from my phone. Please excuse my brevity.

On October 21, 2015 1:30:46 PM GMT+02:00, Alexander Shenkin <ashenkin at ufl.edu> wrote:
>Hello all,
>
>I've been banging my head over what must be a simple solution.  I would
>
>like to apply a function across columns of a dataframe for rows grouped
>
>across different columns.  These groups are not exclusive.  See below 
>for an example.  Happy to use dplyr, data.table, or whatever.  Any 
>guidance appreciated!
>
>Thanks,
>Allie
>
>
>desired algorithm: calculate a/(a+b) for each TRUE and FALSE grouping
>of 
>columns grp1 and grp2.
>
>this_df = data.frame(a = c(1,2,3,4,5), b = c(7,8,9,10,11), grp1 = 
>c(T,T,F,F,F), grp2 = c(F,T,F,T,F))
>
>desired output (doesn't have to be exactly this format, but something 
>along these lines):
>
>grp1 T 0.166
>grp1 F 0.286
>grp2 T 0.25
>grp2 F 0.25
>
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