function [H2]=xyrecur_ave(He,niter)
%
% Returns the gridded data on a grid of half the size
% with the data "averaged" to the cell-centers.
%
% e.g.
%      [H2]=xyrecur_ave(He,niter);

H2=He;

% Recursively iterate
for nit=1:niter,

[nx,ny]=size(H2);
disp(sprintf(' Recursion level %i (%i,%i) -> (%i,%i) ... ',nit,nx,ny,nx/2,ny/2));

ii=1:2:nx-1;
jj=1:2:ny-1;

H2=(H2(ii,jj)+H2(ii+1,jj)+H2(ii,jj+1)+H2(ii+1,jj+1))/4;

disp('done.');

end