title: How to save Pandas pie plot to a file?
body: <p>I have the following code:</p>
  
  <pre><code>import pandas as pd
  import matplotlib
  matplotlib.style.use('ggplot')
  df = pd.DataFrame({ 'sample1':['foo','bar','bar','qux'], 'score':[5,9,1,7]})
  sum_df = df.groupby("sample1").sum()
  pie = sum_df.plot(kind="pie", figsize=(6,6), legend = False, use_index=False, subplots=True, colormap="Pastel1")
  </code></pre>
  
  <p>Which makes the pie chart. What I want to do then is to save it to a file.
  But why this fail?</p>
  
  <pre><code>fig = pie.get_figure()
  fig.savefig("~/Desktop/myplot.pdf")
  </code></pre>
  
  <p>I get this error:</p>
  
  <pre><code>'numpy.ndarray' object has no attribute 'get_figure'
  </code></pre>