TITLE(arrows @@ Add Arrows to a Plot)
USAGE(
arrows(x0, y0, x1, y1, length=0.25, angle=30,
        code=2, col, lty)
)
ALIAS(arrows)
VALUE(
This function is invoked for its side effect.
It draws an arrow between the point LANG((x0[i], y0[i]))
and the point LANG((x1[i],y1[i])).  LANG(length) gives the length of the
edges of the arrow head (in inches) and angle specifies the angle
from the shaft of the arrow to the edge of the arrow head.  If
LANG(code=2) an arrowhead is drawn at LANG((x0[i],y0[i])) and if
LANG(code=1) an arrowhead is drawn at LANG((x1[i],y1[i])).  If
LANG(code=3) a head is drawn at both ends of the arrow.
PARA
The graphical parameters LANG(col) and LANG(lty) can be used
to specify a color an line texture for the line segments which
make up the arrows (LANG(col) may be a vector).
)
