R: Line graph of a graph

make_line_graph {igraph} | R Documentation

## Line graph of a graph

### Description

This function calculates the line graph of another graph.

### Usage

    make_line_graph(graph)

    line_graph(...)

### Arguments

`graph` | The input graph, it can be directed or undirected.
`...` | Passed to `make_line_graph`.

### Details

The line graph `L(G)` of a `G` undirected graph is defined as follows. `L(G)` has one vertex for each edge in `G` and two vertices in `L(G)` are connected by an edge if their corresponding edges share an end point.

The line graph `L(G)` of a `G` directed graph is slightly different, `L(G)` has one vertex for each edge in `G` and two vertices in `L(G)` are connected by a directed edge if the target of the first vertex's corresponding edge is the same as the source of the second vertex's corresponding edge.

### Value

A new graph object.

### Author(s)

Gabor Csardi csardi.gabor@gmail.com, the first version of the C code was written by Vincent Matossian.

### Examples

    # generate the first De-Bruijn graphs
    g <- make_full_graph(2, directed=TRUE, loops=TRUE)
    make_line_graph(g)
    make_line_graph(make_line_graph(g))
    make_line_graph(make_line_graph(make_line_graph(g)))

[Package igraph version 1.2.4.1 Index]