double frac(nj, ni) ;
		frac:long_name = "fraction of cell that is active" ;
		frac:coordinates = "xc yc" ;
		frac:note = "1: fully active, 0: inactive, (0,1) partially active" ;

 frac =
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 ;