| x
	  (PLFLT *, input)	    Pointer to set of x coordinate values at which the function is
	    evaluated.
	  y
	  (PLFLT *, input)	    Pointer to set of y coordinate values at which the function is
	    evaluated.
	  z
	  (PLFLT **, input)	    Pointer to a vectored two-dimensional array with set of
	    function values.
	  nx
	  (PLINT, input)	    Number of x values at
	    which function is evaluated.
	  ny
	  (PLINT, input)	    Number of y values at
	    which function is evaluated.
	  opt
	  (PLINT, input)	    Determines the way in which the surface is represented. To specify
            more than one option just add the options, e.g. FACETED + SURF_CONT
	     		  opt=FACETED: Network
		  of lines is drawn connecting points at which function is
		  defined.
				  opt=BASE_CONT: A contour
                  plot is drawn at the base XY plane using parameters
                  nlevel and clevel.
				  opt=SURF_CONT: A contour
                  plot is drawn at the surface plane using parameters
                  nlevel and clevel.
				  opt=DRAW_SIDES: draws a curtain
                  between the base XY plane and the borders of the plotted function.
				  opt=MAG_COLOR:
		  the surface is colored according to the value of Z; if
		  MAG_COLOR is not used, then the default
		  the surface is colored according to the intensity of the
		  reflected light in the surface from a light source whose
		  position is set using pllightsource.
clevel
	  (PLFLT *, input)	    Pointer to the array that defines the contour level spacing.
	  nlevel
	  (PLINT, input)          Number of elements in the clevel array.
	  
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