title: One legend for all subplots in pyplot
body: <p>I am currently plotting the same data but visualizing it differently in two subplots (see figure):
  <img src="https://i.stack.imgur.com/hlncy.png" alt="Scatter and horizontal bar plot"></p>
  
  <p>Code snippet used for producing the above figure:</p>
  
  <pre><code># Figure
  plt.figure(figsize=(14,8), dpi=72)
  plt.gcf().suptitle(r'Difference between TI and $\lambda$D', size=16)
  # Subplot 1
  ax1 = plt.subplot2grid((1,3),(0,0),colspan=2)
  
  # Plot scattered data in first subplot
  plt.scatter(LE_x, LE_y, s=40, lw=0, color='gold', marker='o', label=r'$\lambda$D')
  plt.scatter(MD_x, MD_y, s=40, lw=0, color='blue', marker='^', label=r'TI')
  
  # Subplot 2
  ax2 = plt.subplot2grid((1,3),(0,2))
  
  plt.barh(vpos1, LE_hist, height=4, color='gold', label=r'$\lambda$D')
  plt.barh(vpos2, MD_hist, height=4, color='blue', label=r'TI')
  
  # Legend
  legend = plt.legend()
  </code></pre>
  
  <p>Is there any way to make the legend show both the scatter dots and the bars? Would this also go per dummy as described <a href="https://stackoverflow.com/questions/11140311/matplotlib-legend-in-separate-subplot">here</a>? Could somebody then please post a minimal working example for this, since I'm not able to wrap my head around this.</p>