bnlearn (version 4.1)

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

Description

Drop, add or set the direction of a directed arc or an 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.

Value

All functions return invisibly an updated copy of x.

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.

Examples

data(learning.test)
res = gs(learning.test)

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