Package edu.cmu.tetrad.search.utils

Class DagIterator

java.lang.Object

edu.cmu.tetrad.search.utils.DagIterator

public class DagIterator
extends Object

Given a graph, lists all DAGs that result from directing the undirected edges in that graph every possible way. Uses a Meek-algorithm-type method.

Version:

$Id: $Id

Author:

josephramsey

Constructor Summary

Constructors

Constructor	Description
DagIterator(Graph CPDAG)	The given CPDAG must be a CPDAG.

Method Summary

Modifier and Type	Method	Description
boolean	hasNext()	Returns true just in case there is still a DAG remaining in the enumeration of DAGs for this pattern.
Graph	next()	Successive calls to this method return successive DAGs in the CPDAG, in a more or less natural enumeration of them in which an arbitrary undirected edge is picked, oriented one way, Meek rules applied, then a remaining unoriented edge is picked, oriented one way, and so on, until a DAG is obtained, and then by backtracking the other orientation of each chosen edge is tried.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

DagIterator

public DagIterator(Graph CPDAG)

The given CPDAG must be a CPDAG. If it does not consist entirely of directed and undirected edges and if it is not acyclic, it is rejected.

Parameters:

CPDAG - a Graph object

Throws:

IllegalArgumentException - if the CPDAG is not a CPDAG.

Method Details

next

public Graph next()

Successive calls to this method return successive DAGs in the CPDAG, in a more or less natural enumeration of them in which an arbitrary undirected edge is picked, oriented one way, Meek rules applied, then a remaining unoriented edge is picked, oriented one way, and so on, until a DAG is obtained, and then by backtracking the other orientation of each chosen edge is tried. Nonrecursive, obviously.

Returns:

a Graph instead of a DAG because sometimes, due to faulty patterns, a cyclic graph is produced, and the end-user may need to decide what to do with it. The simplest thing is to construct a DAG (Dag(graph)) and catch an exception.

hasNext

public boolean hasNext()

Returns true just in case there is still a DAG remaining in the enumeration of DAGs for this pattern.

Returns:

true just in case there is still a DAG remaining in the enumeration of DAGs for this pattern.