fit2null

  FIT2NULL - calculate the null (anti-preferred) response from a fit to direction

   NULL=FIT2NULL(RESPONSE)

   Given the RESPONSE of a double gaussian fit, return the response 180 degrees
   away from the location with the maximum response.  This is the null
   response or the response in the anti-preferred direction.

   RESPONSE is a 360x2 vector of responses. The first row indicates the 
   angles of the fit, and the second row indicates the responses.

   For backwards compatibility, if RESPONSE is a 360x1 vector, a new first
   row is added equal to 0:359.

   See also: FIT2PREF, FIT2ORTH