title: Pandas plot x or index_column in descending order
body: <p>I wanted to do some plots based on imported csv files from a chemical analysis. So I import as follows:</p>
  
  <pre><code>In [91]:
  
  df = pd.read_csv('/file_location/Untitled 1.csv', delimiter = '\;', index_col = 'IR')
  df
  
  Out[91]:
  Sample 1    Sample 2
  IR      
  300 1   0
  400 5   4
  500 6   0
  600 0   8
  4 rows × 2 columns
  
  
  
   In [98]:
  
  df.plot()
  </code></pre>
  
  <p>Fine looks good.</p>
  
  <p>By convention this type of data i plotted with the x axis in descending order. Highest number to the right (do not ask me why). So i reorder the index-col:</p>
  
  <pre><code>In [97]:
  
  df2 = df.sort_index(axis=0, ascending=False, kind='quicksort')
  df2
  Out[97]:
  Sample 1    Sample 2
  IR      
  600 0   8
  500 6   0
  400 5   4
  300 1   0
  4 rows × 2 columns
  </code></pre>
  
  <p>Awesome!</p>
  
  <pre><code>In [96]:
  
  df2.plot()
  Out[96]:
  </code></pre>
  
  <p>But when i Plot it looks the same (/sadpanda)</p>
  
  <p>Any ideas =)?</p>