[igraph] How to Add Colorbar to Graph

[Lorenzo Isella]

Dear All,
Please consider the code snippet at the end of the email.
It generates a network, highlights the diameter and paints each node 
according to a discrete variable I call "time". 
There are a few things I would like to add to the generated pdf
(1) A colorbar, possible showing 8 discrete colors corresponding to the 
8 possible values of my "time" variable
(2) I would like to be able to give a title to the colorbar
(3) I would like to be able to write some text corresponding to each 
color, to briefly explain what it stands for (I do not want to read 
simply 1,2...8 for each value in "time")
(4) I also need the possibility of fine-tuning the size of the text I 
want to add to the plot, just to make sure it is readable in a figure 
for a publication.

Any help with (1)-(4) above is really appreciated.
Cheers

Lorenzo




library(Cairo)
library(igraph)

set.seed(1234)

g <- erdos.renyi.game(80, 1/20)

n_col <- 8

my_seq <- rep(seq(n_col),10)

colbar <- rainbow(n_col)

V(g)$time <- my_seq

l <- layout.fruchterman.reingold(g)
l <- layout.norm(l, -1,1, -1,1)

CairoPDF("graph_with_colors.pdf")

plot(g, layout=l,
    vertex.label.dist=0.5,   vertex.color=colbar[V(g)$time],
    vertex.frame.color="#ff000033", 
edge.color="#55555533",vertex.label=NA, vertex.size=4
    )



d <- get.diameter(g,weights=NA)

V(g)$id <- seq(vcount(g))-1
g2 <- subgraph(g, d)
plot(g2, layout=l[ V(g2)$id+1, ],
vertex.color=colbar[V(g2)$time], vertex.frame.color="#ff000033",
  edge.color="#555555",vertex.label=NA, edge.width=2, vertex.size=4,
  add=TRUE, rescale=FALSE)



dev.off()