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#!/usr/bin/env python
"""
An example that shows how to add your own positions to nodes
and have graphviz "neato" position the edges.
miles_graph() returns an undirected graph over the 128 US cities from
the datafile miles_dat.txt.
This example is described in Section 1.1 in Knuth's book [1][2].
The data used in this example is copied from [2]. The filename and
header have been modified to adhere to the request of the author to
not corrupt the original source file content and name.
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 absolute_import
from __future__ import unicode_literals
from __future__ import print_function
from __future__ import division
import fileinput
__author__ = """Aric Hagberg (aric.hagberg@gmail.com)"""
def miles_graph():
"""Return a graph from the data in miles_dat.txt.
Edges are made between cities that are less then 300 miles apart.
"""
import math
import re
import gzip
G=pgv.AGraph(name='miles_dat')
G.node_attr['shape']='circle'
G.node_attr['fixedsize']='true'
G.node_attr['fontsize']='8'
G.node_attr['style']='filled'
G.graph_attr['outputorder']='edgesfirst'
G.graph_attr['label']="miles_dat"
G.graph_attr['ratio']='1.0'
G.edge_attr['color']='#1100FF'
G.edge_attr['style']='setlinewidth(2)'
cities=[]
for line in gzip.open("miles_dat.txt.gz",'rt'):
if line.startswith("*"): # skip comments
continue
numfind=re.compile("^\d+")
if numfind.match(line): # this line is distances
dist=line.split()
for d in dist:
if float(d) < 300: # connect if closer then 300 miles
G.add_edge(city,cities[i])
i=i+1
else: # this line is a city, position, population
i=1
(city,coordpop)=line.split("[")
cities.insert(0,city)
(coord,pop)=coordpop.split("]")
(y,x)=coord.split(",")
G.add_node(city)
n=G.get_node(city)
# assign positions, scale to be something reasonable in points
n.attr['pos']="%f,%f)"%(-(float(x)-7000)/10.0,(float(y)-2000)/10.0)
# assign node size, in sqrt of 1,000,000's of people
d=math.sqrt(float(pop)/1000000.0)
n.attr['height']="%s"%(d/2)
n.attr['width']="%s"%(d/2)
# assign node color
n.attr['fillcolor']="#0000%2x"%(int(d*256))
# empty labels
n.attr['label']=' '
return G
if __name__ == '__main__':
import warnings
import pygraphviz as pgv
# ignore Graphviz warning messages
warnings.simplefilter('ignore', RuntimeWarning)
G=miles_graph()
print("Loaded miles_dat.txt containing 128 cities.")
G.write("miles.dot")
print("Wrote miles.dot")
G.draw("miles.png",prog='neato',args='-n2')
print("Wrote miles.png")
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