Alternatively, if the displacement table is in ???last row number??? format, the null range indicating no instances of value number r is given by Displacement_Table(r,c)=Displacement_Table(r???1,c) (if r???1 is a valid row number), or, for r equals the lowest valid row number, Displacement_Table(r,c)=0 (for 1-based row numbering) or ???1 (for zero-based row numbering). 159.