DCL:GRPH2:UDPACK: Contour Routines: Explanation of Subroutines
Sets the value of the contour level used by udcntr (or udcntz) by the minimum & maximum values and step size, or by the number of levels.
NumRu::DCL.udgcla(xmin,xmax,dx)
xmin, xmax (R) The minimum and maximum values of the contour levels. The levels do not necessarily need to have conveniently rounded numbers. dx (R) When dx < 0, uses dx as the step size. When dx=0, inquires 'NLEV' and generates approximately nlev contour levels. When dx > 0, generates approximately INT(ABS(DX)) contour levels.