% example_quiver.m
% 繪制矢量圖
[X,Y]=meshgrid(-2:.2:2);
Z=X.*exp(-X.^2 - Y.^2+1);
% 得到X，Y位置處的向量
[DX,DY]=gradient(Z,.2,.2);
% 繪制等值線圖
contour(X,Y,Z)
hold on
% 疊加矢量分布圖
quiver(X,Y,DX,DY)
colormap hsv
hold off
title('figure: vector and contour')