R: Ancestral graph

isAG {ggm} | R Documentation

## Ancestral graph

### Description

Check if it is an adjacency matrix of an ancestral graph

### Usage

    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

    	## 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)

[Package ggm version 2.3 Index]