Use this if you are using igraph from R
| complementer {igraph} | R Documentation | 
A complementer graph contains all edges that were not present in the input graph.
complementer(graph, loops = FALSE)
graph | 
 The input graph, can be directed or undirected.  | 
loops | 
 Logical constant, whether to generate loop edges.  | 
complementer creates the complementer of a graph. Only edges
which are not present in the original graph will be included in the
new graph.
complementer keeps graph and vertex attriubutes, edge
attributes are lost.
A new graph object.
Gabor Csardi csardi.gabor@gmail.com
## Complementer of a ring
g <- make_ring(10)
complementer(g)
## A graph and its complementer give together the full graph
g <- make_ring(10)
gc <- complementer(g)
gu <- union(g, gc)
gu
graph.isomorphic(gu, make_full_graph(vcount(g)))