title: How to do interpolation on datetime and float
body: <p>I am doing 1d interpolation using <a href="http://docs.scipy.org/doc/scipy/reference/tutorial/interpolate.html#d-interpolation-interp1d" rel="nofollow">scipy</a> on time-series. My x-axis data is in datetime format and y axis is in float like:</p>
  
  <pre><code>3/15/2012 16:00:00  32.94
  3/16/2012 16:00:00  32.95
  3/19/2012 16:00:00  32.61
  </code></pre>
  
  <p>Now during slope calculation <code>slope = (y_hi-y_lo) / (x_hi-x_lo)</code> i am getting the error <code>TypeError: unsupported operand type(s) for /: 'float' and 'datetime.timedelta'</code> which is an obvious error. Can someone point me toward the right direction, How to handle it ?</p>