How to find chromatic number of graph in R?

Question

I have the adjacency matrix of the graph (graph theory). First of all, I want to get the chromatic number of this graph (the smallest number of colors needed to color the vertices of a graph so that no two adjacent vertices share the same color). Then I want to get colors (like groups: from 1 to 4 maximum) of the vertices. Is it possible to get it in R using the igraph package? Thanks a lot.

Answer 1

You can use the greedy_vertex_coloring() function to estimate the chromatic number.

library(igraph)
set.seed(44)
n = 8
m <- t(matrix(c(
0,0,0,0,0,0,0,1,
1,0,0,0,0,0,0,0,
1,0,0,1,1,0,0,0,
0,0,1,0,0,1,1,0,
0,1,1,0,0,0,0,0,
0,0,0,0,0,0,0,0,
1,1,0,0,1,0,0,1,
0,1,0,0,0,1,0,0),ncol=n))
g1 <- graph_from_adjacency_matrix(m, weighted=TRUE, mode="directed")
ch_number <- max(greedy_vertex_coloring(g1))