
plvpas: Specify viewport using coordinates and aspect ratio 

DESCRIPTION:

    This function is used in example 9. 

SYNOPSIS:

plvpas(xmin, xmax, ymin, ymax, aspect)

ARGUMENTS:

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

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

    ymin (PLFLT, input) :    The normalized subpage coordinate of the
    bottom edge of the viewport. 

    ymax (PLFLT, input) :    The normalized subpage coordinate of the top
    edge of the viewport. 

    aspect (PLFLT, input) :    Ratio of length of y axis to length of x
    axis. 
