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%功能：多重x\y轴曲线的绘制

%输入：向量x1,y1,x2,y2

%输出：在同一个曲线图中，有两套x坐标轴（可以的话可以做两套y轴）

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x1=1:10;

y1=1:10;

x2=1:10;

y2=5:14;

hl1 = line(x1,y1,'Color','r');%第一条曲线的绘制，以默认的主x\y轴为坐标

ax1 = gca;%设置主坐标轴的颜色，用默认的位置，设定颜色

set(ax1,'XColor','r','YColor','r')

%创建第二套坐标轴，设定颜色及位置

ax2=axes('Position',get(ax1,'Position'),...

           'XAxisLocation','top',...

           'YAxisLocation','right',...

           'Color','none',...

           'XColor','k','YColor','k');

hl2 = line(x2,sin(x2),'Color','k','Parent',ax2);%第二条曲线的绘制，以ax2为坐标系

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注意：

（1）改变x1\y1\x2\y2就可以实现plotyy()和plotxx()的功能；

（2）因为line()\axes()为low_level函数，因此都是在主窗口句柄中绘制，不会产生子窗口，所以当想多增添一条曲线时，直接再用line()函数即可，不用像plot()那样还得用hold on语句。