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"""
===========
Lanl Routes
===========
Routes to LANL from 186 sites on the Internet.
The data file can be found at:
- https://github.com/networkx/networkx/blob/main/examples/graphviz_layout/lanl_routes.edgelist
This example needs Graphviz and PyGraphviz.
"""
import matplotlib.pyplot as plt
import networkx as nx
def lanl_graph():
"""Return the lanl internet view graph from lanl.edges"""
try:
fh = open("lanl_routes.edgelist")
except OSError:
print("lanl.edges not found")
raise
G = nx.Graph()
time = {}
time[0] = 0 # assign 0 to center node
for line in fh.readlines():
(head, tail, rtt) = line.split()
G.add_edge(int(head), int(tail))
time[int(head)] = float(rtt)
# get largest component and assign ping times to G0time dictionary
Gcc = sorted(nx.connected_components(G), key=len, reverse=True)[0]
G0 = G.subgraph(Gcc)
G0.rtt = {}
for n in G0:
G0.rtt[n] = time[n]
return G0
G = lanl_graph()
print(G)
print(nx.number_connected_components(G), "connected components")
plt.figure(figsize=(8, 8))
# use graphviz to find radial layout
pos = nx.nx_agraph.graphviz_layout(G, prog="twopi", root=0)
# draw nodes, coloring by rtt ping time
options = {"with_labels": False, "alpha": 0.5, "node_size": 15}
nx.draw(G, pos, node_color=[G.rtt[v] for v in G], **options)
# adjust the plot limits
xmax = 1.02 * max(xx for xx, yy in pos.values())
ymax = 1.02 * max(yy for xx, yy in pos.values())
plt.xlim(0, xmax)
plt.ylim(0, ymax)
plt.show()
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