Question

I can add 2 y-axis to a octave/matlab plot but when I try and add the x-axis at the bottom of the plot with xlabel(‘Frequency in Hz’) it doesn’t show up

[ax h1 h2]=plotyy(xx,yy,xx,yy2); %plot two y axes and 1 x-axis
axes(ax(1)); ylabel('Phase Angle in degrees');
axes(ax(2)); ylabel('Amplitude');

Anybody know how to fix this so the x-axis will also show up

I’m using octave 3.2.4 / matlab

Answer 1

Make sure to call xlabel() after referencing one of the specific axes on the plot. You just need to do it once, but because of the double axis, invoking x-label outside of a specific axis context won’t work. The following works for me just fine in Octave 3.2.4.

xx  = [1,2,3]; 
yy  = [10,11,12]; 
yy2 = [-10,-11,-12]; 

[ax h1 h2]=plotyy(xx,yy,xx,yy2); 

axes(ax(1)); xlabel('Frequency in Hz'); ylabel('Phase Angle in degrees');
axes(ax(2)); ylabel('Amplitude');