How do I create multiple axis objects in a GUI using MATLAB 7.7 (R2008b)?

I would like to plot data with two y-axes inside a GUI, by creating two different axis objects (I cannot use PLOTYY). The first axis object already exists in the GUI. I am able to create a second axis object in the GUI, however, when I try to set the 'Position' property of the second axis to match that of the first, the second axis is no longer visible.

Answer 1

[MathWorks Support Team]

The reason that you are unable to see both axes is that the units for the position of the axes created by GUIDE are initialized differently than axes created within a function or at the MATLAB command prompt. An axis created by GUIDE has the 'Units' property set as 'character' by default while an axis created in a script or function has the 'Units' property set as 'normalized' by default. To resolve this issue, you need to set the 'Units' property of an axis created later to 'character', and then set the position. The following code demonstrates the idea discussed above. It has been adapted from the "Using Multiple X- and Y-Axes" demo and uses the 'testGUI' files attached below.

testGUI %create the GUI containing an axis

ax1 = findall(0, 'type', 'axes'); %assumes the axis inside the GUI is the only axis

set(get(ax1, 'Parent'), 'HandleVisibility', 'on'); %set handle visibility to on

axes(ax1); %make ax1 the current axis

x1 = [0:.1:40];

y1 = 4.*cos(x1)./(x1+2);

x2 = [1:.2:20];

y2 = x2.^2./x2.^3;

hl1 = line(x1,y1,'Color','r'); %plot a line in the current axis

set(ax1,'XColor','r','YColor','r'); %set the axis colors of ax1

ax2 = axes('Units', 'character'); %create a new axis and set units to be character

set(ax2, 'Position',get(ax1,'Position'),...

             'XAxisLocation','top',...

             'YAxisLocation','right',...

             'Color','none',...

             'XColor','k','YColor','k'); %position the new axis on the earlier existing axis

hl2 = line(x2,y2,'Color','k','Parent',ax2); %plot a line on the new axis