function vg(fname)  [nx, ny, x, y] = fload(fname);  xmin = min(x);  xmax = max(x);  ymin = min(y);  ymax = max(y);  xdiff = xmax - xmin;  ydiff = ymax - ymin;  diff = max([xdiff ydiff]) / 20.0;  xmin = xmin - diff;  xmax = xmax + diff;  ymin = ymin - diff;  ymax = ymax + diff;    figure;  title(fname);  hold on;  axis([xmin xmax ymin ymax]);  axis image;    fill([xmin xmin xmax xmax], [ymin ymax ymax ymin], [0.7 0.7 0.7]);    ix = 1;  for (j = 1:ny-1)    for (i = 1:nx-1)      i1 = ix;      i2 = ix + 1;      i3 = ix + nx + 1;      i4 = i3 - 1;      xx = [x(i1) x(i2) x(i3) x(i4)];      yy = [y(i1) y(i2) y(i3) y(i4)];      sum = x(i1) + x(i2) + x(i3) + x(i4);      if ~isnan(sum)	fill(xx, yy, [1 1 1]);      end      ix = ix + 1;    end    ix = ix + 1;  end  returnfunction [nx, ny, x, y] = fload(fname);  f = fopen(fname);  if (f < 0)    return;  end    nx = 0;  ny = 0;  x = [];  y = [];    str = fgetl(f);  [n, count] = sscanf(str, '## %d x %d');  if (count == 2 & n(1) > 0 & n(2) > 0)    nx = n(1);    ny = n(2);    [xy] = fscanf(f, '%f', [2,inf]);    x = xy(1,:);    y = xy(2,:);  end    fclose(f);  return