Source code for networkx.algorithms.moral

r"""Function for computing the moral graph of a directed graph."""

import itertools

from networkx.utils import not_implemented_for

__all__ = ["moral_graph"]


[docs]@not_implemented_for("undirected") def moral_graph(G): r"""Return the Moral Graph Returns the moralized graph of a given directed graph. Parameters ---------- G : NetworkX graph Directed graph Returns ------- H : NetworkX graph The undirected moralized graph of G Raises ------ NetworkXNotImplemented If `G` is undirected. Examples -------- >>> G = nx.DiGraph([(1, 2), (2, 3), (2, 5), (3, 4), (4, 3)]) >>> G_moral = nx.moral_graph(G) >>> G_moral.edges() EdgeView([(1, 2), (2, 3), (2, 5), (2, 4), (3, 4)]) Notes ----- A moral graph is an undirected graph H = (V, E) generated from a directed Graph, where if a node has more than one parent node, edges between these parent nodes are inserted and all directed edges become undirected. https://en.wikipedia.org/wiki/Moral_graph References ---------- .. [1] Wray L. Buntine. 1995. Chain graphs for learning. In Proceedings of the Eleventh conference on Uncertainty in artificial intelligence (UAI'95) """ H = G.to_undirected() for preds in G.pred.values(): predecessors_combinations = itertools.combinations(preds, r=2) H.add_edges_from(predecessors_combinations) return H