MATLAB: Plotyy making extra lines

plottingplottyy

Hello,
I am using plotyy to plot some data. The problem is that when I plot more thant 2 sets of data in one of the y axis, it appears straight lines linking the end point of the ploted data to the origin of the axis. Here is a minimal code that produces the same result.
 figure
x=0:0.1:10;
y1=-x;
y2=5*x.^2/1000;
y3=1.2*x.^2/1000;
[ax,p1,p2] = plotyy(x,y1,[x,x],[y2,y3],'plot','plot');
Any ideas on how to solve this? Thank you in advance.
Best regards,
Simão Nóbrega

Best Answer

Main reason is because you're concatenating the two arrays [x x] and [y2 y3] as they are 1xN each so in the code you're just plotting like
 X=[x x]; %which is now 1x2N
 Y23 = [y2 y3] %which is also 1x2N
 figure,plot(X,Y23)
to plot more you'll have to make put then as columns.
 [ax,p1,p2] = plotyy(x,y1,[x',x'],[y2',y3'],'plot','plot');
the extra line is connecting the last point [x(end),y2(end)] and [x(1), y3(1)] together.
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