I have a circular layout igraph. I want the vertex label to be displayed outside the circular region. Tried playing around the vertex.label.cex and vertex.label.degree but did not work. Please advice!
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vertex.label.degree takes some serious (but straightforward) tweaking to do this. Here's an example from this gist. It's not my code (it's @kieran's, I believe), but it's a fully working example.
### 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)
1
Here's an example of how to rotate the labels around the circle (see this gist):
## One way to rotate text labels.
library(igraph)
### Example
## Generate some fake data
n <- 75
g <- erdos.renyi.game(n, 0.5)
V(g)$name = paste("long_name", 1:n, sep="_")
## Obviously labeling in this way this only makes sense for graphs
## laid out as a circle to begin with
la <- layout.circle(g)
par(mar=c(8,6,6,6))
plot(g, layout=la, vertex.size=2, vertex.label="")
## Apply labels manually
#Specify x and y coordinates of labels, adjust outward as desired
x = la[,1]*1.3
y = la[,2]*1.3
#create vector of angles for text based on number of nodes
# (flipping the orientation of the words half way around so none appear
# upside down)
angle = ifelse(atan(-(la[,1]/la[,2]))*(180/pi) < 0,
90 + atan(- (la[,1]/la[,2]))*(180/pi), 270 + atan(-la[,1]/la[,2])*(180/pi))
#Apply the text labels with a loop with angle as srt
for (i in 1:length(x)) {
text(x=x[i], y=y[i], labels=V(g)$name[i], adj=NULL,
pos=NULL, cex=.7, col="black", srt=angle[i], xpd=T)
}
Alicia
- 11
- 1
0
This is a very useful example but it does not solve all of my problems. Look at this small change in the GitHub code:
### Here's one way to do it.
library(igraph)
library(ggplot2)
## 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 <- 75
g <- erdos.renyi.game(n, 0.5)
V(g)$name = "long_name"
## 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)
At the top and and the bottom the labels become basically unreadable because they overlap. Any suggestions on how to change the code to fix this issue?
Mauro
- 1