.BG
.VE $Header: /usr3/s/current/s/.help/RCS/segments,v 1.2 83/12/30 19:34:17 rab Exp $
.FN segments
.FN arrows
.TL
segments arrows: Plot Disconnected Line Segments or Arrows
.CS
segments(x1, y1, x2, y2)
arrows(x1, y1, x2, y2, size, open, rel)
.PP
.AG x1,y1,x2,y2
co-ordinates of the end-points of the segments or arrows.  Lines
will be drawn from `(x1[i],y1[i])' to `(x2[i],y2[i])'.
Missing values (NAs) are allowed.
.AG size
width of the arrowhead as a fraction of the length of the arrow
if `rel' is TRUE.
If `rel' is FALSE, `size' is arrowhead width in inches.
Default 0.2.
.AG open
logical, if TRUE the arrowhead is "v" shaped, if FALSE (default)
it is diamond shaped.
.AG rel
logical, should arrowhead be sized relative to the length of the
arrow?  Default FALSE.
.PP
Graphical parameters may also be supplied as arguments to this
function (see `par').
.PP
Note the distinction from `lines' which draws a curve (connected line
segments).
Any segments with any NAs as end-points will not be drawn.
.EX
# draw arrows from `i'th to `i+1st points
s <- seq(len(x)-1)  # sequence one shorter than x
arrows( x[s], y[s], x[s+1], y[s+1] )
.KW plot*
.KW aplot*
.WR
