title: Bar graph values missing matplotlib
body: <p>My code-</p>
  
  <pre><code>import pandas as pd
  import numpy as np 
  import matplotlib.pyplot as plt
  
  plt.figure()
  cols = ['hops','frequency']
  data = [[-13,1],[-8,1],[-5,1],[0,2],[2,1],[4,1],[7,1]]
  data = np.asarray(data)
  indices = np.arange(0,len(data))
  
  plot_data = pd.DataFrame(data, index=indices, columns=cols)
  
  plt.bar(plot_data['hops'].tolist(),plot_data['frequency'].tolist(),width=0.8)
  plt.xlim([-20,20])
  plt.ylim([0,20])
  plt.ylabel('Frequency')
  plt.xlabel('Hops')
  </code></pre>
  
  <p>Output-</p>
  
  <p><a href="https://i.stack.imgur.com/MBFfy.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MBFfy.png" alt="enter image description here"></a></p>
  
  <p>My requirements-
  I want the graph to have the scale X axis-[-20,20],Y axis [0,18] and the bars should be labelled like in this case the 1st bar should be numbered 1 in this case and so on.</p>