possAn {pcalg}

Find possible ancestors of given node(s).

Description

In a DAG, CPDAG, MAG or PAG determine which nodes are (possible) ancestors of x on definite status or just any paths potentially avoiding given nodes on the paths.

Usage

possAn(m, x, y = NULL, possible = TRUE, ds = TRUE,
type = c("cpdag", "pdag", "dag", "mag", "pag"))

Arguments

m

Adjacency matrix in coding according to type.

x

Node positions of starting nodes.

y

Node positions of nodes through which a path must not go.

possible

If TRUE, possible ancestors are returned.

ds

If TRUE, only paths of definite status are considered.

type

Type of adjacency matrix in m. The coding is according to amatType.

Details

Not all possible combinations of the arguments are currently implemented and will issue an error if called.

Value

Vector of all node positions found as (possible) ancestors of the nodes in x.

Author(s)

Markus Kalisch

See Also

amatType

Examples

## a -- b -> c
amat <- matrix(c(0,1,0, 1,0,1, 0,0,0), 3,3)
colnames(amat) <- rownames(amat) <- letters[1:3]
plot(as(t(amat), "graphNEL"))

possAn(m = amat, x = 3, possible = TRUE, ds = FALSE, type = "pdag") ## all nodes
possAn(m = amat, x = 3, y = 2, possible = TRUE, ds = FALSE, type = "pdag") ## only node 1