arcops: Drop, add or set the direction of an arc or an edge

In bnlearn: Bayesian Network Structure Learning, Parameter Learning and Inference

Drop, add or set the direction of an arc or an edge

Description

Drop, add or set the direction of a directed or undirected arc (also known as edge).

Usage

# arc operations.
set.arc(x, from, to, check.cycles = TRUE, check.illegal = TRUE, debug = FALSE)
drop.arc(x, from, to, debug = FALSE)
reverse.arc(x, from, to, check.cycles = TRUE, check.illegal = TRUE, debug = FALSE)

# edge (i.e. undirected arc) operations
set.edge(x, from, to, check.cycles = TRUE, check.illegal = TRUE, debug = FALSE)
drop.edge(x, from, to, debug = FALSE)

Arguments

x	an object of class bn.
from	a character string, the label of a node.
to	a character string, the label of another node.
check.cycles	a boolean value. If TRUE the graph is tested for acyclicity; otherwise the graph is returned anyway.
check.illegal	a boolean value. If TRUE arcs that break the parametric assumptions of x, such as those from continuous to discrete nodes in conditional Gaussian networks, cause an error.
debug	a boolean value. If TRUE a lot of debugging output is printed; otherwise the function is completely silent.

Details

The set.arc() function operates in the following way:

• if there is no arc between from and to, the arc from \rightarrow to is added.

• if there is an undirected arc between from and to, its direction is set to from \rightarrow to.

• if the arc to \rightarrow from is present, it is reversed.

• if the arc from \rightarrow to is present, no action is taken.

The drop.arc() function operates in the following way:

• if there is no arc between from and to, no action is taken.

• if there is a directed or an undirected arc between from and to, it is dropped regardless of its direction.

The reverse.arc() function operates in the following way:

• if there is no arc between from and to, it returns an error.

• if there is an undirected arc between from and to, it returns an error.

• if the arc to \rightarrow from is present, it is reversed.

• if the arc from \rightarrow to is present, it is reversed.

The set.edge() function operates in the following way:

• if there is no arc between from and to, the undirected arc from - to is added.

• if there is an undirected arc between from and to, no action is taken.

• if either the arc from \rightarrow to or the arc to \rightarrow from are present, they are replaced with the undirected arc from - to.

The drop.edge() function operates in the following way:

• if there is no undirected arc between from and to, no action is taken.

• if there is an undirected arc between from and to, it is removed.

• if there is a directed arc between from and to, no action is taken.

Value

All functions return invisibly an updated copy of x.

Author(s)

Marco Scutari

Examples

dag = cpdag(model2network("[A][C][F][B|A][D|A:C][E|B:F]"))
dag

## use debug = TRUE to get more information.
updated = set.arc(dag, "A", "B")
updated
updated = drop.arc(dag, "A", "B")
updated
updated = drop.edge(dag, "A", "B")
updated
updated = reverse.arc(dag, "A", "D")
updated

bnlearn documentation built on Aug. 21, 2025, 5:42 p.m.