> I'm trying to avoid using nested loops in the following code but I'm > not sure how to proceed. Any help would be greatly appreciated. > With regards,Phil > X = matrix(rnorm(100), 10, 10) > result = 0 > for(m in 1:nrow(X)){ > for(n in 1:ncol(X)){ > if(X[m,n] != 0){ > result = result + (X[m,n] / (1 + abs(m - n))) > } > } > } First, you don't need the 'if', do you? If X[m,n]==0 (rare for a floating point number) (X[m,n] / (1 + abs(m - n)) will be zero anyway.
Then, depending on the matrix size, you can probably do the whole thing using an index array. Something like: idx <- as.matrix( expand.grid(1:nrow(X), 1:ncol(X)) ) result <- sum( X[idx] / apply(idx,1, function(x) 1+abs(diff(x))) ) #... which seemed to do the identically the same thing as your loop when I tried it. S Ellison ******************************************************************* This email and any attachments are confidential. Any use...{{dropped:8}} ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.