title: Bold font weight for LaTeX axes label in matplotlib
body: <p>In <a href="http://matplotlib.org/"><code>matplotlib</code></a> you can make the text of an axis label bold by</p>
  
  <pre><code>plt.xlabel('foo',fontweight='bold')
  </code></pre>
  
  <p>You can also use LaTeX with the right backend</p>
  
  <pre><code>plt.xlabel(r'$\phi$')
  </code></pre>
  
  <p>When you combine them however, the math text is not bold anymore</p>
  
  <pre><code>plt.xlabel(r'$\phi$',fontweight='bold')
  </code></pre>
  
  <p>Nor do the following LaTeX commands seem to have any effect</p>
  
  <pre><code>plt.xlabel(r'$\bf \phi$')
  plt.xlabel(r'$\mathbf{\phi}$')
  </code></pre>
  
  <p><strong>How can I make a bold <code>$\phi$</code> in my axis label?</strong></p>