75 lines
2.1 KiB
Python
75 lines
2.1 KiB
Python
# See https://github.com/networkx/networkx/pull/1474
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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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"""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 = {
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"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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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(
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f'unknown triad name "{triad_name}"; use one of the triad names'
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" in the TRIAD_NAMES constant"
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)
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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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