#!/usr/bin/env python
"""
Build a directed graph of 1022 categories and
5075 cross-references as defined in the 1879 version of Roget's Thesaurus
contained in the datafile roget_dat.txt. This example is described in
Section 1.2 in Knuth's book [1,2].
Note that one of the 5075 cross references is a self loop yet
it is included in the graph built here because
the standard networkx DiGraph class allows self loops.
(cf. 400pungency:400 401 403 405).
References.
----------
[1] Donald E. Knuth,
"The Stanford GraphBase: A Platform for Combinatorial Computing",
ACM Press, New York, 1993.
[2] http://www-cs-faculty.stanford.edu/~knuth/sgb.html
"""
from __future__ import print_function
# Authors: Brendt Wohlberg, Aric Hagberg (hagberg@lanl.gov)
# Date: 2005-04-01 07:56:22 -0700 (Fri, 01 Apr 2005)
# Copyright (C) 2004-2016 by
# Aric Hagberg <hagberg@lanl.gov>
# Dan Schult <dschult@colgate.edu>
# Pieter Swart <swart@lanl.gov>
# All rights reserved.
# BSD license.
from networkx import *
import re
import sys
def roget_graph():
""" Return the thesaurus graph from the roget.dat example in
the Stanford Graph Base.
"""
# open file roget_dat.txt.gz (or roget_dat.txt)
import gzip
fh=gzip.open('roget_dat.txt.gz','r')
G=DiGraph()
for line in fh.readlines():
line = line.decode()
if line.startswith("*"): # skip comments
continue
if line.startswith(" "): # this is a continuation line, append
line=oldline+line
if line.endswith("\\\n"): # continuation line, buffer, goto next
oldline=line.strip("\\\n")
continue
(headname,tails)=line.split(":")
# head
numfind=re.compile("^\d+") # re to find the number of this word
head=numfind.findall(headname)[0] # get the number
G.add_node(head)
for tail in tails.split():
if head==tail:
print("skipping self loop",head,tail, file=sys.stderr)
G.add_edge(head,tail)
return G
if __name__ == '__main__':
from networkx import *
G=roget_graph()
print("Loaded roget_dat.txt containing 1022 categories.")
print("digraph has %d nodes with %d edges"\
%(number_of_nodes(G),number_of_edges(G)))
UG=G.to_undirected()
print(number_connected_components(UG),"connected components")