title: How to add a line on a pandas bar plot in matplotlib?
body: <p>Hi I have managed to add a line in a bar plot however the position is not right. I want to make the points right in the middle of each bar. Could anyone help?</p>
  
  <pre><code>&gt;&gt;&gt; df
     price       cost        net
  0   22.5 -20.737486   1.364360
  1   35.5 -19.285862  16.695847
  2   13.5 -20.456378  -9.016052
  3    5.0 -19.643776 -17.539636
  4   13.5 -27.015138 -15.964597
  5    5.0 -24.267836 -22.618819
  6   18.0 -21.096404  -7.357684
  7    5.0 -24.691966 -24.116106
  8    5.0 -25.755958 -22.080329
  9   25.0 -26.352161  -2.781588
  
  fig = plt.figure()
  df[['price','cost']].plot(kind = 'bar',stacked = True,color = ['grey','navy'])
  df['net'].plot('o',color = 'orange',linewidth=2.0,use_index = True)
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/v9jhT.png" alt="enter image description here"></p>