title: Filter pandas DataFrame columns
body: <p>I have a DataFrame like this:</p>
  
  <pre><code>             A        B        C        D      
  2000-01-03 -0.59885  0.18141 -0.68828  0.77572
  2000-01-04  0.83935  0.15993  0.95911 -1.12959
  2000-01-05  2.80215 -0.10858 -1.62114 -0.20170
  2000-01-06  0.71670 -0.26707  1.36029  1.74254
  </code></pre>
  
  <p>I would like to filter the columns based on the value of the first row.
  E.g. I want to take only the columns where the first value is >0. and the result I expect is this:</p>
  
  <pre><code>             B        D      
  2000-01-03  0.18141  0.77572
  2000-01-04  0.15993 -1.12959
  2000-01-05 -0.10858 -0.20170
  2000-01-06 -0.26707  1.74254
  </code></pre>
  
  <p><strong>Update</strong>
  Thanks to Jeff suggestion I wrote this code:</p>
  
  <pre><code>cols = []
  firstRow = df.ix[0,:]
  for i in range(len(firstRow)):
      if firstRow[i]&gt;0:
      cols.append(i) 
  return df.ix[:, list(cols)].values.copy()   
  </code></pre>
  
  <p>Is there a more elegant way to do this?</p>