title: Seaborn regplot with colorbar?
body: <p>I'm plotting something with seaborn's <code>regplot</code>. As far as I understand, it uses <code>pyplot.scatter</code> behind the scenes. So I assumed that if I specify colour for scatterplot as a sequence, I would then be able to just call <code>plt.colorbar</code>, but it doesn't seem to work:</p>
  
  <pre><code>sns.regplot('mapped both', 'unique; repeated at least once', wt, ci=95, logx=True, truncate=True, line_kws={"linewidth": 1, "color": "seagreen"}, scatter_kws={'c':wt['Cis/Trans'], 'cmap':'summer', 's':75})
  plt.colorbar()
  
  Traceback (most recent call last):
  
    File "&lt;ipython-input-174-f2d61aff7c73&gt;", line 2, in &lt;module&gt;
      plt.colorbar()
  
    File "/usr/local/lib/python2.7/dist-packages/matplotlib/pyplot.py", line 2152, in colorbar
      raise RuntimeError('No mappable was found to use for colorbar '
  
  RuntimeError: No mappable was found to use for colorbar creation. First define a mappable such as an image (with imshow) or a contour set (with contourf).
  </code></pre>
  
  <p>Why doesn't it work, and is there a way around it?</p>
  
  <hr>
  
  <p>I would be fine with using size of the dots instead of colour if there was an easy way to generate a legend for the sizes</p>