Cost matrix from an array without for loop.

Hi I want to create a matrix with entries the absolute value between each point in an array.

My array is called domain, and it has length grid_number.

I have done this in the below code, however I have used a for loop. It takes a long time to run when grid_number is large. Is there a neat way to do this?

for i=1:grid_number
    for j=1:grid_number
       cost(i,j)=abs(domain(i)-domain(j))
    end
end

Answer 1

[the cyclist]

You can use implicit expansion to subtract the two vector from each other, by transposing one of them.

cost = abs(domain-domain.');

If you have an older version of MATLAB, that does not support implicit expansion, you can use

cost = abs(bsxfun(@minus,domain,domain'));

Answer 2

[Matt J]

cost=abs( domain(:)-domain(:).' );