igraph (version 1.3.5)

make_line_graph: Line graph of a graph

Description

This function calculates the line graph of another graph.

Usage

make_line_graph(graph)
line_graph(...)

Value

A new graph object.

Arguments

graph

The input graph, it can be directed or undirected.

...

Passed to make_line_graph.

Author

Gabor Csardi , the first version of the C code was written by Vincent Matossian.

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.

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)))