Add a Box Around a Plot
DESCRIPTION:
Surrounds the current plot with a box of given thickness.
USAGE: 
box(n=1, fill=F)
OPTIONAL ARGUMENTS:
n:
number of times the box is drawn (i.e., the heaviness of the line).
fill:
logical flag. Should the entire plot region be filled with a solid color (TRUE) or just outlined (FALSE)?

Graphical parameters may also be supplied as arguments to this function (see par). In particular the bty parameter controls the type of box.

SIDE EFFECTS:
a box is drawn at the usual position of the axes. The width of the box depends on the device that is being used.
SEE ALSO:
par , polygon .
EXAMPLES: 
box(5, col=2)   # draw a thick color 2 box around plot
box(fill=T, col=7)   # draw a filled box in color 7