Assign colour to chosen communities in a plot - r

Question

In a plot, I need to colour two specific communities. Take the following data frame:
A B C D E F G
A 0 1 0 1 0 1 0
B 1 0 1 1 0 1 0
C 0 1 0 0 0 0 0
D 1 1 0 0 1 1 0
E 0 0 0 1 0 1 0
F 1 1 0 1 1 0 1
G 0 0 0 0 0 1 0
ob <- read.csv("...ties.csv",sep = ",", header = TRUE, row.names = 1)
m <- as.matrix(ob)
g <- graph.adjacency(m, mode="undirected", weighted = T, add.rownames = T)
First, I detect the communities (com) of my graph g using edge.betweenness:
com <- edge.betweenness.community(g)
V(g)$memb <- com$membership
This operation produces a number of communities, com[[1]],com[[2]], etc. I plot the resulting graph -- each community one colour -- with the following code:
plot(g, vertex.color=membership(com))
Now, how do I colour only two chosen communities, say com[[1]] and com[[2]], keeping the rest of the nodes homogeneous?

Answer 1

I had to tweak your adjacency matrix so that more than 1 community showed up.
library(igraph)
ob <- read.table(text="
A B C D E F G
A 0 1 0 1 0 1 0
B 1 0 1 1 0 1 0
C 0 0 0 0 0 0 0
D 1 1 0 0 1 0 0
E 0 0 0 1 0 1 1
F 0 1 0 0 1 0 1
G 0 0 0 0 1 1 0", header=TRUE)
m <- as.matrix(ob)
g <- graph.adjacency(m, mode="undirected", weighted = T, add.rownames = T)
com <- edge.betweenness.community(g)
V(g)$memb <- com$membership
cols <- membership(com)
cols[cols!=3] <- 1
plot(g, vertex.color=cols)