%例8-22  使用quiver函數繪制箭頭圖形。

>> % 該程序用于繪制箭頭圖形
>> [x,y] = meshgrid(-2:.2:2,-1:.15:1);
>> z = x .* exp(-x.^2 + y.^2); 
>> [px,py] = gradient(z,.2,.15);
>> contour(x,y,z)
>>hold on
>> quiver(x,y,px,py)
>>hold off
>>axis image
>>