| 
            plvpas
          ( | xmin , | 
| xmax , | |
| ymin , | |
| ymax , | |
| aspect ); | 
      Device-independent routine for setting up the viewport.  The viewport
      is chosen to be the largest with the given aspect ratio that fits
      within the specified region (in terms of normalized subpage
      coordinates).  This routine is functionally equivalent to plvpor
      when a ``natural'' aspect ratio (0.0) is chosen.  Unlike plvasp,
      this routine reserves no extra space at the edges for labels.
    
xmin
          (PLFLTThe normalized subpage coordinate of the left-hand edge of the viewport.
xmax
          (PLFLTThe normalized subpage coordinate of the right-hand edge of the viewport.
ymin
          (PLFLTThe normalized subpage coordinate of the bottom edge of the viewport.
ymax
          (PLFLTThe normalized subpage coordinate of the top edge of the viewport.
aspect
          (PLFLTRatio of length of y axis to length of x axis.
      Redacted form: plvpas(xmin, xmax, ymin, ymax, aspect)
    
This function is used in example 9.