title: Pandas panel data
body: <p>I have a python panel that is index by integer values. 
  in dict form it would look like this:</p>
  
  <pre><code>{1:{1:series,2: series,3:series,4:series} 2:{1:series,2:series,3:series,4:series}...}
  </code></pre>
  
  <p>I would like to roll through my data by date and on each date take a time slice in the past apply a function to every time series so I get a result such as this where X is the output of the function of timeslice.</p>
  
  <pre><code>  1 2 3 4 ...
  1 X X X X
  2 X X X X
  3 X X X X
  4 X X X X
  </code></pre>
  
  <p>I thought <code>pandas.Panel.apply(func)</code> would do this but it does not.  I  only get a result in 1 seemingly random column.   I can iterate with for loops but i was hoping there was a faster and easier way of doing this.</p>
  
  <p>I have a panel that looks like this:</p>
  
  <pre><code> &lt;class 'pandas.core.panel.Panel'&gt;
   Dimensions: 1000 (items) x 3714 (major) x 1000 (minor)
   Items: 1 to 1000
   Major axis: 1997-09-10 00:00:00 to 2012-06-19 00:00:00  
   Minor axis: 1 to 1000
  </code></pre>