title: MatPlotLib - Showing legend
body: <p>I'm making a scatter plot from a Pandas <code>DataFrame</code> with 3 columns. The first two would be the <code>x</code> and <code>y</code> axis, and the third would be classicfication data that I want to visualize by points having different colors. My question is, how can I add the legend to this plot:</p>
  
  <pre><code>df= df.groupby(['Month', 'Price'])['Quantity'].sum().reset_index()
  df.plot(kind='scatter', x='Month', y='Quantity', c=df.Price , s = 100, legend = True);
  </code></pre>
  
  <p>As you can see, I'd like to automatically color the dots based on their price, so adding labels manually is a bit of an inconvenience. Is there a way I could add something to this code, that would also show a legend to the <code>Price</code> values?</p>
  
  <p>Also, this colors the scatter plot dots on a range from black to white. Can I add custom colors without giving up the easy usage of <code>c=df.Price</code>?</p>
  
  <p>Thank you!</p>