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#!/usr/bin/env python
"""
Atlas of all graphs of 6 nodes or less.
"""
__author__ = """Aric Hagberg (hagberg@lanl.gov)"""
__date__ = "$Date: 2005-05-19 14:23:02 -0600 (Thu, 19 May 2005) $"
__credits__ = """"""
__revision__ = ""
# Copyright (C) 2004 by
# Aric Hagberg <hagberg@lanl.gov>
# Dan Schult <dschult@colgate.edu>
# Pieter Swart <swart@lanl.gov>
# Distributed under the terms of the GNU Lesser General Public License
# http://www.gnu.org/copyleft/lesser.html
from networkx import *
from networkx.generators.atlas import *
from networkx.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=graph_atlas_g()[0:208] # 208
# remove isolated nodes, only connected graphs are left
U=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.delete_node(n)
U=disjoint_union(U,G)
# list of graphs of all connected components
C=connected_component_subgraphs(U)
UU=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=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__':
from networkx import *
G=atlas6()
print "graph has %d nodes with %d edges"\
%(number_of_nodes(G),number_of_edges(G))
print number_connected_components(G),"connected components"
try: #drawing
import pylab as P
P.figure(1,figsize=(8,8))
# layout graphs with positions using graphviz neato
pos=graphviz_layout(G,prog="neato")
# color nodes the same in each connected subgraph
C=connected_component_subgraphs(G)
for g in C:
c=P.array([random.random()]*number_of_nodes(g)) # random color...
draw(g,
pos,
node_size=40,
node_color=c,
vmin=0.0,
vmax=1.0,
with_labels=False
)
P.savefig("atlas.png",dpi=75)
except:
pass
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