Package edu.cmu.tetrad.search.utils

Class DiscriminatingPath

java.lang.Object

edu.cmu.tetrad.search.utils.DiscriminatingPath

public class DiscriminatingPath
extends Object

Represents a discriminating path in a graph. The triangles that must be oriented this way (won't be done by another rule) all look like the ABC triangle below, where the dots are a collider path from E to B (excluding E and B but including A) with each node on the collider path a parent of C. The orientation of A *-* B *-* C is not a feature of the discriminating path. Note that if there is not a circle at B, the path no longer needs to be oriented by the rule. Whether the path exists in a given graph and is as yet unoriented can be checked with the existsAndUnorientedIn method.

          B
         *o           * is either an arrowhead or a circle; note B *-> A is not a condition in Zhang's rule
        /  \
       v    v
 E....A --> C
 

This is equivalent to Zhang's rule R4. (Zhang, J. (2008). On the completeness of orientation rules for causal discovery in the presence of latent confounders and selection bias. Artificial Intelligence, 172(16-17), 1873-1896.) A similar rule was originally given in Spirtes et al. (1993). Note that as in Zhang, the discriminating path itself is E...A, B, C. We refer to the part of this path between E to B as the 'collider path.' The collider path is included in any sepset of E and C. Note also that in Zhang's tail-complete version of the rule, the arrow endpoint B *-> A is not a condition of the rule, as in previous code, so we do not check for it.

The idea is that if we know that E is independent of C given all the nodes on the collider path plus perhaps some other nodes in the graph, then there should be a collider at B; otherwise, there should be a noncollider at B. If there should be a collider at B, we orient A *-> B <-> C; otherwise, we orient A *-* B -> C.

Author:

josephramsey

See Also:

• existsIn(Graph)

Constructor Summary

Constructors

Constructor	Description
DiscriminatingPath(Node x, Node w, Node v, Node y, LinkedList<Node> colliderPath, boolean checkEcNonadjacency)	Represents a discriminating path construct in a graph.

Method Summary

Modifier and Type	Method	Description
boolean	existsIn(Graph graph)	Checks this discriminating path construct to make sure it is a discriminating path in the given graph.
List<Node>	getColliderPath()	Returns the collider subpath of the discriminating path.
Node	getV()	Returns the node B in the discriminating path.
Node	getW()	Retrieves the node A in the discriminating path.
Node	getX()	Returns the node E in the discriminating path.
Node	getY()	Returns the node C in the discriminating path.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Details

DiscriminatingPath

public DiscriminatingPath(Node x,
 Node w,
 Node v,
 Node y,
 LinkedList<Node> colliderPath,
 boolean checkEcNonadjacency)

Represents a discriminating path construct in a graph. A discriminating path is a path in a graph that meets certain criteria, as explained in the class documentation. This class stores the nodes in the discriminating path, as well as a reference to collider subpath of the discriminating path itself, which consists of all the nodes between E and B along the discriminating path, excluding E and B but including A. These nodes need to be included in any sepset of E and C in the graph, which can be checked.

Parameters:

x - the node X in the discriminating path

w - the node W in the discriminating path

v - the node V in the discriminating path

y - the node Y in the discriminating path

colliderPath - the collider subpath of the discriminating path

checkEcNonadjacency - whether to check that E is not adjacent to C

Method Details

existsIn

public boolean existsIn(Graph graph)

Checks this discriminating path construct to make sure it is a discriminating path in the given graph. See the class documentation, above, for a description of the requirements.

Parameters:

graph - the graph to check

Returns:

true if the discriminating path construct is valid, false otherwise.

getX

public Node getX()

Returns the node E in the discriminating path.

Returns:

the node E in the discriminating path.

getW

public Node getW()

Retrieves the node A in the discriminating path.

Returns:

the node A in the discriminating path

getV

public Node getV()

Returns the node B in the discriminating path.

Returns:

the node B in the discriminating path.

getY

public Node getY()

Returns the node C in the discriminating path.

Returns:

the node C in the discriminating path.

getColliderPath

public List<Node> getColliderPath()

Returns the collider subpath of the discriminating path.

Returns:

the collider subpath of the discriminating path.

toString

public String toString()

Overrides:

toString in class Object