title: Log-Log plot of pandas dataframe
body: <p>I would like to make a log-log plot with pandas</p>
  
  <pre><code>import numpy as np
  import pandas as pd
  x =  10**arange(1, 10)
  y = 10** arange(1,10)*2
  df1 = pd.DataFrame( data=y, index=x )
  df2 = pd.DataFrame(data = {'x': x, 'y': y})
  df1.plot(logy=True, logx=True)    
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/akoq2.png" alt="df1.plot(logy=True, logx=True)"></p>
  
  <p>How can I make the x-axis logarithmic?</p>