title: cannot plot with matplotlib and pandas
body: <p>I am using OSX (Mojave 10.14.3) and am having a strange issue plotting a <code>pandas (0.24.2)</code> dataframe using <code>matplotlib (3.0.3)</code>. I am using python <code>3.7.3</code>.</p>
  
  <p>So, the code is as:</p>
  
  <pre><code>import pandas as pd
  import matplotlib.pyplot as plt
  
  df = pd.DataFrame({
                    'name':['john','mary','peter','jeff','bill','lisa','jose'],
                    'age':[23,78,22,19,45,33,20],
                    'gender':['M','F','M','M','M','F','M'],
                    'state':['california','dc','california','dc','california','texas','texas'],
                    'num_children':[2,0,0,3,2,1,4],
                    'num_pets':[5,1,0,5,2,2,3]
                    })
  
  df.plot(kind='scatter',x='num_children',y='num_pets',color='red')
  plt.show()
  </code></pre>
  
  <p>All this does is show an empty window with nothing in it. I was expecting a scatterplot with 7 points. The example is taken from the web tutorial as is.</p>
  
  <p><strong>EDIT</strong></p>
  
  <pre><code>plt.savefig('myfilename.png')
  </code></pre>
  
  <p>Savefig works.</p>