Add Arrows or Segments to a Plot

network.arrow draws a segment or arrow between two pairs of points; unlike arrows or segments, the new plot element is drawn as a polygon.

Usage

network.arrow(
  x0,
  y0,
  x1,
  y1,
  length = 0.1,
  angle = 20,
  width = 0.01,
  col = 1,
  border = 1,
  lty = 1,
  offset.head = 0,
  offset.tail = 0,
  arrowhead = TRUE,
  curve = 0,
  edge.steps = 50,
  ...
)

Arguments

x0: A vector of x coordinates for points of origin
y0: A vector of y coordinates for points of origin
x1: A vector of x coordinates for destination points
y1: A vector of y coordinates for destination points
length: Arrowhead length, in current plotting units
angle: Arrowhead angle (in degrees)
width: Width for arrow body, in current plotting units (can be a vector)
col: Arrow body color (can be a vector)
border: Arrow border color (can be a vector)
lty: Arrow border line type (can be a vector)
offset.head: Offset for destination point (can be a vector)
offset.tail: Offset for origin point (can be a vector)
arrowhead: Boolean; should arrowheads be used? (Can be a vector))
curve: Degree of edge curvature (if any), in current plotting units (can be a vector)
edge.steps: For curved edges, the number of steps to use in approximating the curve (can be a vector)
...: Additional arguments to polygon

Value

None.

Details

network.arrow provides a useful extension of segments and arrows when fine control is needed over the resulting display. (The results also look better.) Note that edge curvature is quadratic, with curve providing the maximum horizontal deviation of the edge (left-handed). Head/tail offsets are used to adjust the end/start points of an edge, relative to the baseline coordinates; these are useful for functions like plot.network, which need to draw edges incident to vertices of varying radii.

Note

network.arrow is a direct adaptation of gplot.arrow from the sna package.

References

Butts, C. T. (2008). “network: a Package for Managing Relational Data in R.” Journal of Statistical Software, 24(2). doi:10.18637/jss.v024.i02

Author

Carter T. Butts buttsc@uci.edu

Examples


  #Plot two points
  plot(1:2,1:2)
  
  #Add an edge
  network.arrow(1,1,2,2,width=0.01,col="red",border="black")