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| # See https://github.com/networkx/networkx/pull/1474 | |
| # Copyright 2011 Reya Group <http://www.reyagroup.com> | |
| # Copyright 2011 Alex Levenson <[email protected]> | |
| # Copyright 2011 Diederik van Liere <[email protected]> | |
| """Functions that generate the triad graphs, that is, the possible | |
| digraphs on three nodes. | |
| """ | |
| import networkx as nx | |
| from networkx.classes import DiGraph | |
| __all__ = ["triad_graph"] | |
| #: Dictionary mapping triad name to list of directed edges in the | |
| #: digraph representation of that triad (with nodes 'a', 'b', and 'c'). | |
| TRIAD_EDGES = { | |
| "003": [], | |
| "012": ["ab"], | |
| "102": ["ab", "ba"], | |
| "021D": ["ba", "bc"], | |
| "021U": ["ab", "cb"], | |
| "021C": ["ab", "bc"], | |
| "111D": ["ac", "ca", "bc"], | |
| "111U": ["ac", "ca", "cb"], | |
| "030T": ["ab", "cb", "ac"], | |
| "030C": ["ba", "cb", "ac"], | |
| "201": ["ab", "ba", "ac", "ca"], | |
| "120D": ["bc", "ba", "ac", "ca"], | |
| "120U": ["ab", "cb", "ac", "ca"], | |
| "120C": ["ab", "bc", "ac", "ca"], | |
| "210": ["ab", "bc", "cb", "ac", "ca"], | |
| "300": ["ab", "ba", "bc", "cb", "ac", "ca"], | |
| } | |
| def triad_graph(triad_name): | |
| """Returns the triad graph with the given name. | |
| Each string in the following tuple is a valid triad name:: | |
| ('003', '012', '102', '021D', '021U', '021C', '111D', '111U', | |
| '030T', '030C', '201', '120D', '120U', '120C', '210', '300') | |
| Each triad name corresponds to one of the possible valid digraph on | |
| three nodes. | |
| Parameters | |
| ---------- | |
| triad_name : string | |
| The name of a triad, as described above. | |
| Returns | |
| ------- | |
| :class:`~networkx.DiGraph` | |
| The digraph on three nodes with the given name. The nodes of the | |
| graph are the single-character strings 'a', 'b', and 'c'. | |
| Raises | |
| ------ | |
| ValueError | |
| If `triad_name` is not the name of a triad. | |
| See also | |
| -------- | |
| triadic_census | |
| """ | |
| if triad_name not in TRIAD_EDGES: | |
| raise ValueError( | |
| f'unknown triad name "{triad_name}"; use one of the triad names' | |
| " in the TRIAD_NAMES constant" | |
| ) | |
| G = DiGraph() | |
| G.add_nodes_from("abc") | |
| G.add_edges_from(TRIAD_EDGES[triad_name]) | |
| return G | |