How to vectorize this "for" loop, or parallel it.

fun = @(x,y) x + x.*y;
N = 1e3;
K = zeros(N);
for i = 1:N
  for j = i:N
      K(i,j) = fun(i, j);
  end
end

Answer 1

[Azzi Abdelmalek]

fun = @(x,y) x + x.*y;
N=1000
[y,x]=meshgrid(1:N,1:N);
out=triu(fun(x,y))

[Azzi Abdelmalek]

N=4000;
tic
fun = @(x,y) x + x.*y;
[y,x]=meshgrid(1:N,1:N);
f=triu(fun(x,y));
toc

tic
K = zeros(N);
for i = 1:N
  for j = i:N
      K(i,j) = fun(i, j);
  end
end
toc
isequal(f,K)

Elapsed time is 0.193062 seconds.  
Elapsed time is 2.421795 seconds.

[chen]

Thanks a lot !

Answer 2

[Matt J]

   K=(1:N).'*(2:N+1);

[Matt J]

Or,

 K=bsxfun(@times,(1:N).', 2:N+1);

On my machine, this is faster than straight multiplcation for some weird reason!!