%%% vfd.m, script for vectorfields
% rha, 26 feb 2004 on vaio
% cf cooper, p. 108
% this exm is gradient of z+(y^2-x^2)/4
[X,Y] = meshgrid(0:.4:2);
U = -X/2;
V = Y/2;
W = 1 + 0*X;
subplot(1,2,1)
for z = [-1, 0, 1]
      Z = z + 0*X;
      quiver3(X,Y,Z,U,V,W)
      hold on
end
axis image