title: How to plot two columns in a dataframe and add legends?
body: <p>i have a question in pandas plotting.  I have a dataframe that contains 4 columns.  How do i plot just two columns and add legends?  The column names are actlow,acthigh,fcstlow,fcsthigh
  so for instance...i want to do this:</p>
  
  <pre><code>    pd.DataFrame.plot(['fcstlow','fcsthigh'],legend=True)
  </code></pre>
  
  <p>Above statement doesn't really plot the legends which is annoying me.  thanks</p>