RGMAP /PERCENT

        [GREG2\]RGMAP /PERCENT P1

    Computes M=MAX(ABS(min),ABS(max)) of the data to be  contoured.  Contour
    levels selected with LEVELS are multiples of P1 percent of M. E.g. if P1
    = 10 and LEVELS 1 2 5 9, the contour levels are 10, 20, 50  and  90%  of
    the peak value.

    From  the  above  rule you can deduce the absolute level values with the
    following commands:
        DEFINE REAL ABSLEVELS /LIKE GREG%LEVELS
        LET ABSLEVELS MAX(ABS(RGMIN),ABS(RGMAX))*P1*GREG%LEVELS/100
        EXA ABSLEVELS