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.
CALL 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.