% m23d.m - m23c via Chebfun

  ff = @(x,y) (1-x).^2 + 100*(y+cos(pi*x)).^2;
  f = chebfun2(ff,[-3 3 -3 3]);
  levels = 0:20:500;
  contour(f,levels), colorbar, grid on
  [minval,minpos] = min2(f);
  x = minpos(1), y = minpos(2)
  hold on, plot(x,y,'.r','markersize',36)