80 lines
2.5 KiB
Python
80 lines
2.5 KiB
Python
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# triads.py - generators for triad graphs
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#
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# Copyright 2015 NetworkX developers.
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# Copyright 2011 Reya Group <http://www.reyagroup.com>
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# Copyright 2011 Alex Levenson <alex@isnotinvain.com>
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# Copyright 2011 Diederik van Liere <diederik.vanliere@rotman.utoronto.ca>
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#
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# This file is part of NetworkX.
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#
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# NetworkX is distributed under a BSD license; see LICENSE.txt for more
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# information.
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"""Functions that generate the triad graphs, that is, the possible
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digraphs on three nodes.
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"""
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from networkx.classes import DiGraph
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__all__ = ['triad_graph']
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#: Dictionary mapping triad name to list of directed edges in the
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#: digraph representation of that triad (with nodes 'a', 'b', and 'c').
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TRIAD_EDGES = {'003': [],
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'012': ['ab'],
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'102': ['ab', 'ba'],
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'021D': ['ba', 'bc'],
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'021U': ['ab', 'cb'],
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'021C': ['ab', 'bc'],
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'111D': ['ac', 'ca', 'bc'],
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'111U': ['ac', 'ca', 'cb'],
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'030T': ['ab', 'cb', 'ac'],
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'030C': ['ba', 'cb', 'ac'],
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'201': ['ab', 'ba', 'ac', 'ca'],
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'120D': ['bc', 'ba', 'ac', 'ca'],
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'120U': ['ab', 'cb', 'ac', 'ca'],
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'120C': ['ab', 'bc', 'ac', 'ca'],
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'210': ['ab', 'bc', 'cb', 'ac', 'ca'],
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'300': ['ab', 'ba', 'bc', 'cb', 'ac', 'ca']
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}
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def triad_graph(triad_name):
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"""Returns the triad graph with the given name.
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Each string in the following tuple is a valid triad name::
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('003', '012', '102', '021D', '021U', '021C', '111D', '111U',
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'030T', '030C', '201', '120D', '120U', '120C', '210', '300')
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Each triad name corresponds to one of the possible valid digraph on
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three nodes.
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Parameters
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----------
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triad_name : string
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The name of a triad, as described above.
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Returns
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-------
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:class:`~networkx.DiGraph`
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The digraph on three nodes with the given name. The nodes of the
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graph are the single-character strings 'a', 'b', and 'c'.
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Raises
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------
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:exc:`ValueError`
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If `triad_name` is not the name of a triad.
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See also
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--------
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triadic_census
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"""
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if triad_name not in TRIAD_EDGES:
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raise ValueError('unknown triad name "{}"; use one of the triad names'
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' in the TRIAD_NAMES constant'.format(triad_name))
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G = DiGraph()
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G.add_nodes_from('abc')
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G.add_edges_from(TRIAD_EDGES[triad_name])
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return G
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