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pcalg (version 2.7-12)

dsep: Test for d-separation in a DAG

Description

This function tests for d-separation of nodes in a DAG.

Usage

dsep(a, b, S=NULL, g, john.pairs = NULL)

Value

TRUE if a and b are d-separated by S in G, otherwise FALSE.

Arguments

a

Label (sic!) of node A

b

Label (sic!) of node B

S

Labels (sic!) of set of nodes on which it is conditioned, maybe empty

g

The Directed Acyclic Graph (object of class "graph", see graph-class from the package graph)

john.pairs

The shortest path distance matrix for all pairs of nodes as computed (also by default) in johnson.all.pairs.sp from package RBGL.

Author

Markus Kalisch (kalisch@stat.math.ethz.ch)

Details

This function checks separation in the moralized graph as explained in Lauritzen (2004).

References

S.L. Lauritzen (2004), Graphical Models, Oxford University Press, Chapter 3.2.2

See Also

dsepTest for a wrapper of this function that can easily be included into skeleton, pc, fci or fciPlus. dsepAM for a similar function for MAGs.

Examples

Run this code
## generate random DAG
p <- 8
set.seed(45)
myDAG <- randomDAG(p, prob = 0.3)
if (require(Rgraphviz)) {
plot(myDAG)
}

## Examples for d-separation
dsep("1","7",NULL,myDAG)
dsep("4","5",NULL,myDAG)
dsep("4","5","2",myDAG)
dsep("4","5",c("2","3"),myDAG)

## Examples for d-connection
dsep("1","3",NULL,myDAG)
dsep("1","6","3",myDAG)
dsep("4","5","8",myDAG)

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