
plwind: Specify world coordinates of viewport boundaries 

DESCRIPTION:

    This function is used in examples 1,2,4,6-12,14-16,18,21,23-27,29,31. 

SYNOPSIS:

plwind(xmin, xmax, ymin, ymax)

ARGUMENTS:

    xmin (PLFLT, input) :    The world x coordinate of the left-hand edge
    of the viewport. 

    xmax (PLFLT, input) :    The world x coordinate of the right-hand edge
    of the viewport. 

    ymin (PLFLT, input) :    The world y coordinate of the bottom edge of
    the viewport. 

    ymax (PLFLT, input) :    The world y coordinate of the top edge of the
    viewport. 
