#!/usr/bin/env python """ Atlas of all graphs of 6 nodes or less. """ __author__ = """Aric Hagberg (hagberg@lanl.gov)""" # Copyright (C) 2004 by # Aric Hagberg # Dan Schult # Pieter Swart # All rights reserved. # BSD license. import networkx as nx #from networkx import * #from networkx.generators.atlas import * from networkx.algorithms.isomorphism.isomorph import graph_could_be_isomorphic as isomorphic import random def atlas6(): """ Return the atlas of all connected graphs of 6 nodes or less. Attempt to check for isomorphisms and remove. """ Atlas=nx.graph_atlas_g()[0:208] # 208 # remove isolated nodes, only connected graphs are left U=nx.Graph() # graph for union of all graphs in atlas for G in Atlas: zerodegree=[n for n in G if G.degree(n)==0] for n in zerodegree: G.remove_node(n) U=nx.disjoint_union(U,G) # list of graphs of all connected components C=nx.connected_component_subgraphs(U) UU=nx.Graph() # do quick isomorphic-like check, not a true isomorphism checker nlist=[] # list of nonisomorphic graphs for G in C: # check against all nonisomorphic graphs so far if not iso(G,nlist): nlist.append(G) UU=nx.disjoint_union(UU,G) # union the nonisomorphic graphs return UU def iso(G1, glist): """Quick and dirty nonisomorphism checker used to check isomorphisms.""" for G2 in glist: if isomorphic(G1,G2): return True return False if __name__ == '__main__': import networkx as nx G=atlas6() print("graph has %d nodes with %d edges"\ %(nx.number_of_nodes(G),nx.number_of_edges(G))) print(nx.number_connected_components(G),"connected components") try: from networkx import graphviz_layout except ImportError: raise ImportError("This example needs Graphviz and either PyGraphviz or Pydot") import matplotlib.pyplot as plt plt.figure(1,figsize=(8,8)) # layout graphs with positions using graphviz neato pos=nx.graphviz_layout(G,prog="neato") # color nodes the same in each connected subgraph C=nx.connected_component_subgraphs(G) for g in C: c=[random.random()]*nx.number_of_nodes(g) # random color... nx.draw(g, pos, node_size=40, node_color=c, vmin=0.0, vmax=1.0, with_labels=False ) plt.savefig("atlas.png",dpi=75)