How can i save all the numbers in an array, generated by an equation inside nested for loop ?

I ve got this nested for loops.. xp1 and yp1 are 500 numbers each.. i am trying to find distance between those points. How can i save all the numbers that a generates in an array..?

 for i = 1:1:numel(xP1)

   for j = 1:1:numel(yP1)

      if(i ~= 500 && j ~= 500)

       a = sqrt((xP1(i) - xP1(i + 1))^2 + ((yP1(j) - yP1(j + 1))^2));

Answer 1

[Azzi Abdelmalek]

k=0
for i = 1:1:numel(xP1)
 for j = 1:1:numel(yP1)

      if(i ~= 500 && j ~= 500)
       k=k+1
       a(k) = sqrt((xP1(i) - xP1(i + 1))^2 + ((yP1(j) - yP1(j + 1))^2));

[Antonio]

Thanks for your answer ... i would like to ask an other question that i just found out... the last element which is the 500th number has to be deducted from 1st element of the array... How can i do that? Thanks in advance...

[Azzi Abdelmalek]

If you mean how to find a(500) from a(1), this is not obvious, I don't see

Answer 2

[Walter Roberson]

a(i,j) = sqrt((xP1(i) - xP1(i + 1))^2 + ((yP1(j) - yP1(j + 1))^2));

Or, more efficiently:

xd = diff(xP1) .^ 2 ;
yd = diff(xP2) .^ 2;
a = sqrt(bsxfun(@plus, xd, yd));

[Walter Roberson]

To handle combining the 500'th and the 1st, the efficient form would be

xd = diff(xP1([1:end 1]));
yd = diff(yP1([1:end 1]));
a = sqrt(bsxfun(@plus, xd, yd));