Plot X vs Y, but with two y-axes for different units

I want to make a time series plot of an estimation error. So time (X) will be on the x-axis and the error (Y) on the y-axis. On the y-axis to the left I want the units of the absolute error (Y), and then I want another y-axis to the right which display the error as a percentage (lets say Y/100). How can I make this work? I guess there is a simple answer! I have tried ployy(x1,y1,x2,y2), but this is not really what I want as I only really got one x and one y - I just want to show the y-range with other numbers to the right... Thanks!

Answer 1

[Mischa Kim]

How about plotyy(x,y,x,y/100)? Of, course you can work with scaling such that you can see both plots reasonably well. In this case you might just want to adjust the labels using something like

 set(get(AX(1),'Ylabel'),'String','y')  
 set(get(AX(2),'Ylabel'),'String','y/100')

where you get AX as an output from the plot command.

[Emilie]

The problem with plotyy is that is creates two lines with different color and matching color on the two y-axes. I basically only got one line, I just want to show a different unit for it on the right y-axis..:/

[Mischa Kim]

I see. Try

figure
x = 0:0.01:20;
y1 = 200*exp(-0.05*x).*sin(x);
y2 = 0.8*exp(-0.5*x).*sin(10*x);
[AX,H1,H2] = plotyy(x,y1,x,y1/100,'plot');

set(get(AX(1),'Ylabel'),'String','Signal') 
set(get(AX(2),'Ylabel'),'String','Signal/100') 

set(H1,'LineStyle','--','Color','r')
set(H2,'LineStyle','none','Color','r')
set(AX,{'ycolor'},{'b';'b'})      % ...and to adjust the axis color

[Emilie]

Thank you so much for the answer, but I got it to work with this script! http://www.mathworks.com/matlabcentral/fileexchange/7426-plot2axes

[Mischa Kim]

That's good to hear. Did the answer solve your problem though? For all the other users with similar questions.