R: Directed graphs

DG {ggm} | R Documentation

## Directed graphs

### Description

Defines the adjacency of a directed graph.

### Usage

    DG(...)

### Arguments

`...` | a sequence of model formulae

### 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.

### 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.

### Author(s)

G. M. Marchetti

### 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)

[Package ggm version 2.3 Index]