[R] Avoiding loops

[Phil Spector]

Here's one way (assuming your data frame is named dat):

    with(dat,
         data.frame(a,t(sapply(a,function(x){
                        apply(dat[a - x >= -5 & a - x <= 0,c('b','c')],2,sum)}))))


 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu



On Tue, 1 Sep 2009, dolar wrote:

>
> Would like some tips on how to avoid loops as I know they are slow in R
>
> i've got a data frame :
>
> a  b  c
> 1  5  2
> 4  6  9
> 5  2  3
> 8  3  2
>
> What i'd like is to sum for each value of a, the sum of b and the sum of c
> where a equal to or less than (with a distance of 5)
>
> i.e. for row three
> we have a=5
> i'd like to sum up b and sum up c with the above rule
> since 5, 4 and 1 are less than (within a distance of 5) or equal to 5, then
> we should get the following result:
>
> a  b   c
> 5  13  14
>
> the overall result should be
> a   b   c
> 1   5   2
> 4   11  11
> 5   13  14
> 8   11  14
>
> how can i do this without a loop?
> --
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> Sent from the R help mailing list archive at Nabble.com.
>
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