for i=1:size(A)   density=A(i,pressPos)*100/(287.05*(A(i,tempPos)));   A(i,windPos)=A(i,windPos)*power(density/densityNormal,1/3);end

density=A(:,pressPos)*100/287.05;density=density/A(:,tempPos);A(:,windPos)=A(:,windPos)*power(density/densityNormal,1/3);

It's difficult to help "optimize" code when you don't know what the code is doing and what the dimensions of the variables are. Make a complete example with actual values, but with manageable sizes, such as just 10 rows instead of 200000.

I second Brother Bob's comment. However, from visual inspection, try using element-wise division with the ./ operator. That might help because it seems in the second code example "density" is a vector and you're trying to divide a vector by a vector. Indexing matrices takes a while with large matrices and the more you can do with matrix-type operations, the faster the code will run.

Also, Matlab was never built for speed. It can run fast, but it's main forte that it tries to use the best algorithms based on your inputs. If you're doing Ax=B and your matrix is symmetric positive definite, you don't have to specifically choose Cholesky over LU decomposition. It should figure that out. If you're looking for speed, try using LAPACK or other such libraries. Your code may still be slower than Matlab's, but at least then you can better optimize it to suit your specific problem.

Hope that helps.

yes the './' operator is what i needed

Thanks