| 
            plot3d
          ( | x , | 
| y , | |
| z , | |
| nx , | |
| ny , | |
| opt , | |
| side ); | 
      Plots a three-dimensional surface plot within the environment set up
      by plw3d.  The surface is defined by the matrix
      
        ,
      the point z[nx][ny]
      z[i][j](.
      Note that the points in vectors x[i],y[j])xyoptplmesh and plot3d is that plmesh draws
      the bottom side of the surface, while plot3d only draws the surface as
      viewed from the top.
    
x
          (PLFLT_VECTORA vector containing the x coordinates at which the function is evaluated.
y
          (PLFLT_VECTORA vector containing the y coordinates at which the function is evaluated.
z
          (PLFLT_MATRIX
	    A matrix containing function values to plot.  Should have
	    dimensions of nx by ny.
          
nx
          (PLINT
            Number of x
ny
          (PLINT
            Number of y
opt
          (PLINTDetermines the way in which the surface is represented:
                  
                    : Lines
                  are drawn showing
                  opt=DRAW_LINEX
                  
                     as a function
                  of z
                  
                     for each
                  value of x
                  
                    .
                y[j]
                  
                  
                    : Lines
                  are drawn showing
                  opt=DRAW_LINEY
                  
                     as a function
                  of z
                  
                     for each
                  value of y
                  
                    .
                x[i]
                  
                  
                    : Network
                  of lines is drawn connecting points at which function is
                  defined.
                opt=DRAW_LINEXY
                  
side
          (PLBOOL
            Flag to indicate whether or not ``sides'' should be draw on the
            figure.  If 
               is true
            sides are drawn, otherwise no sides are drawn.
          side
            
      Redacted form: plot3d(x, y, z, opt, side)
    
This function is used in examples 11 and 21.