title: Adding an x axis label with 2 y axis labels
body: <p>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 <strong>xlabel('Frequency in Hz')</strong> it doesn't show up </p>
  
  <pre><code>[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');
  </code></pre>
  
  <p>Anybody know how to fix this so the x-axis will also show up</p>
  
  <p>I'm using octave 3.2.4 / matlab</p>