How can I write this code lines faster?

Hi,

I need to write a double summation but with a normal cycle for I have the wrong resut.

Th5=double_summation(m,n)=1/((m^2/a^2)+(n^2/b^2))^2

m=(1,3,5); n=(1,3,5).

for m=(1:2:5)

    for n=(1:2:5)
summation(m,n)=1/((m^2/a^2)+(n^2/b^2))^2;
    end
end

To get the corret solution I wrote the entire summation like this, but I can't figure out the problem with the cycle.

S1=1/((1/a^2)+(1/b^2))^2;
S3=S1+(1/((3/a^2)+(1/b^2))^2)+(1/((1/a^2)+(3^2/b^2))^2)+(1/((3^2/a^2)+(3^2/b^2))^2);
S5=S3+(1/((1/a^2)+(5/b^2))^2)+(1/((5^2/a^2)+(1/b^2))^2)+(1/((3^2/a^2)+(5^2/b^2))^2)+(1/((5^2/a^2)+(3^2/b^2))^2)+(1/((5^2/a^2)+(5^2/b^2))^2);

If anyone could help me I would be grateful.

Answer 1

[Walter Roberson]

Your code works, but it leaves 0s inside the array because it never assigns to even rows or columns. But the zeros do not matter if you are just going to sum() the results.

For faster execution vectorize.

 m=(1:2:5).'
 n=1:2:5
 s=1./((m.^2./a.^2)+(n.^2./b.^2)).^2;
 sum(s(:))