Add Loops to a Plot

network.loop draws a "loop" at a specified location; this is used to designate self-ties in plot.network.

Usage

network.loop(
  x0,
  y0,
  length = 0.1,
  angle = 10,
  width = 0.01,
  col = 1,
  border = 1,
  lty = 1,
  offset = 0,
  edge.steps = 10,
  radius = 1,
  arrowhead = TRUE,
  xctr = 0,
  yctr = 0,
  ...
)

Arguments

x0: a vector of x coordinates for points of origin.
y0: a vector of y coordinates for points of origin.
length: arrowhead length, in current plotting units.
angle: arrowhead angle (in degrees).
width: width for loop body, in current plotting units (can be a vector).
col: loop body color (can be a vector).
border: loop border color (can be a vector).
lty: loop border line type (can be a vector).
offset: offset for origin point (can be a vector).
edge.steps: number of steps to use in approximating curves.
radius: loop radius (can be a vector).
arrowhead: boolean; should arrowheads be used? (Can be a vector.)
xctr: x coordinate for the central location away from which loops should be oriented.
yctr: y coordinate for the central location away from which loops should be oriented.
...: additional arguments to polygon.

Value

None.

Details

network.loop is the companion to network.arrow; like the latter, plot elements produced by network.loop are drawn using polygon, and as such are scaled based on the current plotting device. By default, loops are drawn so as to encompass a circular region of radius radius, whose center is offset units from x0,y0 and at maximum distance from xctr,yctr. This is useful for functions like plot.network, which need to draw loops incident to vertices of varying radii.

Note

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

Author

Carter T. Butts buttsc@uci.edu

Examples


#Plot a few polygons with loops
plot(0,0,type="n",xlim=c(-2,2),ylim=c(-2,2),asp=1)
network.loop(c(0,0),c(1,-1),col=c(3,2),width=0.05,length=0.4,
  offset=sqrt(2)/4,angle=20,radius=0.5,edge.steps=50,arrowhead=TRUE)
polygon(c(0.25,-0.25,-0.25,0.25,NA,0.25,-0.25,-0.25,0.25), 
    c(1.25,1.25,0.75,0.75,NA,-1.25,-1.25,-0.75,-0.75),col=c(2,3))