is.triangulated {RBGL} | R Documentation

## Decide if a graph is triangulated

### Description

Decide if a graph is triangulated

### Usage

    is.triangulated(g)

### Arguments

`g` | an instance of the `graph` class

### Details

An undirected graph G = (V, E) is triangulated (i.e. chordal) if all cycles [v1, v2, ..., vk] of length 4 or more have a chord, i.e., an edge [vi, vj] with j != i +/- 1 (mod k)

An equivalent definition of chordal graphs is:

G is chordal iff either G is an empty graph, or there is an v in V such that

1. the neighborhood of v (i.e., v and its adjacent nodes) forms a clique, and

2. recursively, G-v is chordal

### Value

The return value is `TRUE` if `g` is triangulated and `FALSE` otherwise. An error is thrown if the graph is not undirected; you might use `ugraph` to compute the underlying graph.

### Author(s)

Li Long <li.long@isb-sib.ch>

### References

Combinatorial Optimization: algorithms and complexity (p. 403) by C. H. Papadimitriou, K. Steiglitz

### Examples

    con1 <- file(system.file("XML/conn.gxl",package="RBGL"), open="r")
    coex <- fromGXL(con1)
    close(con1)

    is.triangulated(coex)

    con2 <- file(system.file("XML/hcs.gxl",package="RBGL"), open="r")
    coex <- fromGXL(con2)
    close(con2)

    is.triangulated(coex)

[Package RBGL version 1.68.0 Index]