causaldag.classes.dag.DAG.vstructures¶

DAG.vstructures() → Set[Tuple][source]¶

Get all v-structures in the graph, i.e., triples of the form (i, k, j) such that i->k<-j and i is not adjacent to j.

Returns:	Return all triples in the graph in a v-structure (aka an immorality). A v-structure is formed when i->j<-k but there is no arc between i and k. Arcs that participate in a v-structure are identifiable from observational data.
Return type:	Set[Tuple]

Example

>>> import causaldag as cd
>>> g = cd.DAG(arcs={(1, 3), (2, 3)})
>>> g.vstructures()
{(1, 3, 2)}