On Wed, Aug 08, 2012 at 06:03:19AM +0000, Ingo Reinhold wrote:
> Hi Jeff, David,
>
> what I'm trying to do is speed the currently used nest for loop
>
> a<-matrix(c(1:6),ncol=3)
> b<-c(1,2,3,4)
>
> result<-matrix(rep(0, times=dim(a)[1]*length(b)),nrow=dim(a)[1])
> for(ii in 1:dim(a)[1]){
> for(jj in 1:length(b)){
> result[ii,jj]<-a[ii,1]+a[ii,3]/b[jj]
> }
> }
>
> giving the result
>
> [,1] [,2] [,3]
> [1,] 1 3 5
> [2,] 2 4 6
Hi.
The printed matrix is "a". The above code yields on my computer
[,1] [,2] [,3] [,4]
[1,] 6 3.5 2.666667 2.25
[2,] 8 5.0 4.000000 3.50
Try the following
out <- a[, 1] + a[, 3] %o% (1/b)
max(abs(out - result))
[1] 4.440892e-16
Hope this helps.
Petr Savicky.
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