How to avoid the two loops with a less memory consumption.

Hello everyone,

I have used two for loops for one problem. Can anyone suggest me a way to avoid the loops and reduce the time. is it possible to calculate A without using a for loop ? I am using R2015a.

for i=1:100000
for j=1:100000
     A(i,j)=exp(-(x(i)-x(j))-(y(i)-y(j)));
end
end

Answer 1

[Stephen23]

A = exp(x(:).'-x(:) + y(:).'-y(:));

This requires MATLAB version >=R2016b. For earlier versions replace the subtraction with bsxfun:

A = exp(bsxfun(@minus,x(:).',x(:)) + bsxfun(@minus,y(:).',y(:)));

Note: avoiding loops will not have "less memory consumption", most likely more.