NetworkX

Source code for networkx.algorithms.distance_measures

# -*- coding: utf-8 -*-
"""
Graph diameter, radius, eccentricity and other properties.
"""
__author__ = "\n".join(['Aric Hagberg (hagberg@lanl.gov)',
                        'Dan Schult(dschult@colgate.edu)'])
#    Copyright (C) 2004-2010 by 
#    Aric Hagberg <hagberg@lanl.gov>
#    Dan Schult <dschult@colgate.edu>
#    Pieter Swart <swart@lanl.gov>
#    All rights reserved.
#    BSD license.

__all__ = ['eccentricity', 'diameter', 'radius', 'periphery', 'center']

import networkx

[docs]def eccentricity(G, v=None, sp=None): """Return the eccentricity of nodes in G. The eccentricity of a node v is the maximum distance from v to all other nodes in G. Parameters ---------- G : NetworkX graph A graph v : node, optional Return value of specified node sp : dict of dicts, optional All pairs shortest path lenghts as a dictionary of dictionaries Returns ------- ecc : dictionary A dictionary of eccentricity values keyed by node. """ nodes=[] if v is None: # none, use entire graph nodes=G.nodes() elif isinstance(v, list): # check for a list nodes=v else: # assume it is a single value nodes=[v] order=G.order() e={} for v in nodes: if sp is None: length=networkx.single_source_shortest_path_length(G,v) L = len(length) else: try: length=sp[v] L = len(length) except TypeError: raise networkx.NetworkXError('Format of "sp" is invalid.') if L != order: msg = "Graph not connected: infinite path length" raise networkx.NetworkXError(msg) e[v]=max(length.values()) if len(e)==1: return list(e.values())[0] # return single value else: return e
[docs]def diameter(G, e=None): """Return the diameter of the graph G. The diameter is the maximum eccentricity. Parameters ---------- G : NetworkX graph A graph e : eccentricity dictionary, optional A precomputed dictionary of eccentricities. Returns ------- d : integer Diameter of graph See Also -------- eccentricity """ if e is None: e=eccentricity(G) return max(e.values())
[docs]def periphery(G, e=None): """Return the periphery of the graph G. The periphery is the set of nodes with eccentricity equal to the diameter. Parameters ---------- G : NetworkX graph A graph e : eccentricity dictionary, optional A precomputed dictionary of eccentricities. Returns ------- p : list List of nodes in periphery """ if e is None: e=eccentricity(G) diameter=max(e.values()) p=[v for v in e if e[v]==diameter] return p
[docs]def radius(G, e=None): """Return the radius of the graph G. The radius is the minimum eccentricity. Parameters ---------- G : NetworkX graph A graph e : eccentricity dictionary, optional A precomputed dictionary of eccentricities. Returns ------- r : integer Radius of graph """ if e is None: e=eccentricity(G) return min(e.values())
[docs]def center(G, e=None): """Return the periphery of the graph G. The center is the set of nodes with eccentricity equal to radius. Parameters ---------- G : NetworkX graph A graph e : eccentricity dictionary, optional A precomputed dictionary of eccentricities. Returns ------- c : list List of nodes in center """ if e is None: e=eccentricity(G) # order the nodes by path length radius=min(e.values()) p=[v for v in e if e[v]==radius] return p