isAG {ggm}

Ancestral graph

Description

Check if it is an adjacency matrix of an ancestral graph

Usage

isAG(amat)

Arguments

amat

An adjacency matrix.

Details

Checks if the following conditions must hold: (i) no undirected edge meets an arrowhead; (ii) no directed cycles; (iii) spouses cannot be ancestors. For details see Richardson and Spirtes (2002).

Value

A logical value, TRUE if it is an ancestral graph and FALSE otherwise.

Author(s)

Giovanni M. Marchetti, Mathias Drton

References

Richardson, T. S. and Spirtes, P. (2002). Ancestral Graph Markov Models. Annals of Statistics, 30(4), 962–1030.

See Also

makeMG, isADMG

Examples

	## Examples from Richardson and Spirtes (2002)
	a1 <- makeMG(dg=DAG(a~b, b~d, d~c), bg=UG(~a*c))
	isAG(a1)    # Not an AG. (a2) p.969
	a2 <- makeMG(dg=DAG(b ~ a, d~c), bg=UG(~a*c+c*b+b*d))           # Fig. 3 (b1) p.969
	isAG(a2)