# See https://github.com/networkx/networkx/pull/1474
# Copyright 2011 Reya Group <http://www.reyagroup.com>
# Copyright 2011 Alex Levenson <alex@isnotinvain.com>
# Copyright 2011 Diederik van Liere <diederik.vanliere@rotman.utoronto.ca>
"""Functions that generate the triad graphs, that is, the possible
digraphs on three nodes.
"""
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"],
}
[docs]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