ggm (version 2.5)

DG: Directed graphs

Description

Defines the adjacency of a directed graph.

Usage

DG(...)

Value

the adjacency matrix of the directed graph, i.e., a square Boolean matrix of order equal to the number of nodes of the graph and a one in position \((i,j)\) if there is an arrow from

\(i\) to \(j\) and zero otherwise. The dimnames of the adjacency matrix are the labels for the nodes of the graph.

Arguments

...

a sequence of model formulae

Author

G. M. Marchetti

Details

The directed graph is defined by a sequence of models formulae. For each formula the response defines a node of the graph and its parents. The graph contains no loops.

References

Lauritzen, S. (1996). Graphical models. Oxford: Clarendon Press.

See Also

DAG, UG

Examples

## A DAG
DG(y ~ x, x ~ z, z ~ u)

## A cyclic directed graph
DG(y ~ x, x ~ z, z ~ y)

## A graph with two arrows between two nodes
DG(y ~ x, x ~ y)

## There can be isolated nodes
DG(y ~ x, x ~ x)