iFit/to_slice

 Create slice object from sqw object

   >> s = to_slice (w)
   >> s = to_slice (w, 'signal','Q')   % make signal equal to |Q| (other options available too)

   w           2D sqw object
   
   'signal'    [Optional] keyword to make the signal axis another coordinate than the intensity.
               Useful to see the variation of e.g. energy across a slice.
               Valid coordinates are: 
                   'h', 'k', 'l'       r.l.u.
                   'E'                 energy transfer
                   'Q'                 |Q|         
%   Overloaded methods:
      sqw/to_slice
      sqw/to_slice