title: Matplotlib plot bar, float() argument must be a string or a number, not 'NoneType'
body: <p>I am showing relevant part of the code</p>
  
  <pre><code>import matplotlib.pyplot as plt
  tacf = pd.DataFrame(data_acf)
  print (type(tacf))
  plt.bar(tacf,height=2.0)
  plt.show()
  </code></pre>
  
  <p>Output</p>
  
  <pre><code>&lt;class 'pandas.core.frame.DataFrame'&gt;
    File "/home/jh/miniconda3/lib/python3.6/site-packages/matplotlib/patches.py", line 351, in set_linewidth
      self._linewidth = float(w)
  TypeError: float() argument must be a string or a number, not 'NoneType'
  </code></pre>
  
  <p>If I go for tacf.head</p>
  
  <pre><code>&lt;bound method NDFrame.head of            0
  0   1.000000
  1   0.942361
  2   0.863303
  3   0.794420
  4   0.727603
  5   0.671579
  6   0.622612
  7   0.570949
  8   0.529410
  9   0.497035
  10  0.485163
  11  0.479443
  12  0.461094
  13  0.444726
  14  0.436634
  </code></pre>
  
  <p>I am confused with bars args and kwargs.
  Should I convert dataframe to different type or..?</p>
  
  <p>How to plot dataframe as a bar with Matplotlib?</p>