title: DataFrame Plot: how to sort X axis
body: <p>I am plotting some counts from a field of dataframe (pandas) and I found that the X axis is sorted by the counts (descending order). Instead is it possible to sort by the alphabetical order of the field?</p>
  
  <p>Here is the Python code:</p>
  
  <pre><code>df['cartype'].value_counts().plot(kind='bar')
  </code></pre>
  
  <p>This sorts by the count but I want to sort by the cartype names. Any solution?</p>