Ancestral graph

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Description

Check if it is an adjacency matrix of an ancestral graph

Usage

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isAG(amat)

Arguments

amat

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

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	## 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)

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