[R] Odp: how to speed up this for loop?

[Petr PIKAL]

Hi

r-help-bounces at r-project.org napsal dne 22.07.2008 01:24:05:

> 
> Could anyone tell me a better way to achieve the output of this for 
loop? It
> seems to run quite slow. I'm sure there must be a more consise way to 
sum
> from FN to LN, excluding positive values, for each row.

It is difficult to understand what you really want as we do not have R, 
FN, LN and Temp.

> vec<-rnorm(100)
> sum(vec[vec<0])
[1] -45.72518

Gives you sum of vec values which are lower than zero. It shall be easy to 
extend it to set of vectors or matrix.

> mat<-rnorm(120)
> dim(mat)<-c(10,12)
> apply(mat, 2, function(x) sum(x[x<0]))
 [1] -0.9543727 -3.9965437 -6.7924017 -1.4949170 -3.8042263 -6.5552674 
-2.6386912 -3.3587444 -6.3740483 -3.1178593 -7.2580333 -3.2709297

There are other options but you shall follow posting guide to obtain 
better answers.

Regards
Petr


> 
> #sum between FN and LN, excluding positive values
> for(i in 1:R){
> for(j in FN[i]:LN[i]){
> if(Temp[i,j]<0)
> sum[i] <- sum[i] + sum(Temp[i,j])}}
> 
> Cheers, 
> R
> -- 
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