functions in split.i - r

             recenter cube on coordinates coor  
 
   EXAMPLE  
   x=span(0,1,15)(,-:1:16)(,,-:1:17);  
   y=span(0,1,16)(-:1:15,)(,,-:1:17);  
   z=span(0,1,17)(-:1:16,)(-:1:15,,);  
   u=abs(x-0.5,y-0.5,z-0.5);  
   v=recenter(u,[3,4,5]);  
   need not be a cube; can be a rectangle or a hypercube  
interpreted function, defined at contrib/split.i   line 604