pcalg (version 2.7-11)

legal.path: Check if a 3-node-path is Legal

Description

Check if the path \(a--b--c\) is legal.

A 3-node path \(a--b--c\) is “legal” iff either \(b\) is a collider or \(a--b--c\) is a triangle.

Usage

legal.path(a, b, c, amat)

Value

TRUE if path is legal, otherwise FALSE.

Arguments

a,b,c

(integer) positions in adjacency matrix of nodes \(a\), \(b\), and \(c\), respectively.

amat

Adjacency matrix (coding 0,1,2,3 for no edge, circle, arrowhead, tail; e.g., amat[a,b] = 2 and amat[b,a] = 3 implies a -> b)

Author

Markus Kalisch ()

Examples

amat <- matrix( c(0,1,1,0,0, 2,0,1,0,0, 2,2,0,2,1,
                  0,0,1,0,0, 0,0,2,0,0), 5,5)
legal.path(1,3,5, amat)
legal.path(1,2,3, amat)
legal.path(2,3,4, amat)