Large loops in R

On Tue, Dec 4, 2012 at 11:27 AM, Charles Novaes de Santana
<charles.santana at gmail.com> wrote:

Dear Michael,

Thank you for your answer.

I have 2 matrices. Each position of the matrices is a weight. And I
need to calculate the following sum of differences:

Considering:
mat1 and mat2 - two matrices (each of them 48000 x 48000).
d1 and d2 - two constant values.

sum<-0;
for(i in 1:nrows1){
                        for(j in 1:nrows2){
                                        sum<-sum+ ( ( (mat1(i,j)/d1) -
(mat2(i,j)/d2) )^2 )
                                }
                        }
                }

I was wondering if there is a better way to do this sum.

sum( (mat1/d1-mat2/d2)^2)

Correct me if I'm wrong though - aren't matrices of 48x times 48k
larger than what R can handle at present?

HTH

Peter