Source code for networkx.algorithms.moral

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

from networkx.utils import not_implemented_for
import itertools

__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 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. References ---------- .. [1] Wray L. Buntine. 1995. Chain graphs for learning. In Proceedings of the Eleventh conference on Uncertainty in artificial intelligence (UAI'95) """ if G is None: raise ValueError("Expected NetworkX graph!") 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