将 vertex.label 放置在 igraph 中的圆形布局之外

我有一个圆形布局 igraph。我希望顶点标签显示在圆形区域之外。尝试玩周围vertex.label.cex and vertex.label.degree但没有用。请指教！

vertex.label.degree需要一些认真的（但简单的）调整才能做到这一点。这是一个例子这个要点。这不是我的代码（它是@kieran的，我相信），但这是一个完全有效的示例。

### Here's one way to do it.

library(igraph)
library(ggplot2)
library(scales)

## The igraph docs say that vertex.label.degree controls the position
## of the labels with respect to the vertices. It's interpreted as a
## radian, like this:
##
## Value is : Label appears ... the node
## -pi/2: above
## 0: to the right of
## pi/2: below
## pi: to the left of
##
## We can generalize this. vertex.label.degree can take a vector as
## well as a scalar for its argument. So we write a function to 
## calculate the right position for a label based on its vertex's location
## on the circle.

## Get the labels aligned consistently around the edge of the circle
## for any n of nodes.
## This code borrows bits of ggplot2's polar_coord function
## start = offset from 12 o'clock in radians
## direction = 1 for clockwise; -1 for anti-clockwise.

radian.rescale <- function(x, start=0, direction=1) {
  c.rotate <- function(x) (x + start) %% (2 * pi) * direction
  c.rotate(scales::rescale(x, c(0, 2 * pi), range(x)))
}

### Example
## Generate some fake data
n <- 15
g <- erdos.renyi.game(n, 0.5)
## Obviously labeling in this way this only makes sense for graphs
## laid out as a circle to begin with
la <- layout.circle(g)

lab.locs <- radian.rescale(x=1:n, direction=-1, start=0)
plot(g, layout=la, vertex.size=2, vertex.label.dist=1,
     vertex.label.degree=lab.locs)