| 
            plwind
          ( | xmin , | 
| xmax , | |
| ymin , | |
| ymax ); | 
Specify the window, i.e., the world coordinates of the edges of the viewport.
xmin
          (PLFLTThe world x coordinate of the left-hand edge of the viewport.
xmax
          (PLFLTThe world x coordinate of the right-hand edge of the viewport.
ymin
          (PLFLTThe world y coordinate of the bottom edge of the viewport.
ymax
          (PLFLTThe world y coordinate of the top edge of the viewport.
      Redacted form: plwind(xmin, xmax, ymin, ymax)
    
This function is used in examples 1, 2, 4, 6-12, 14-16, 18, 21, 23-27, 29, and 31.