Graphs from adjacency lists {igraph}R Documentation

Create graphs from adjacency lists

Description

An adjacency list is a list of numeric vectors, containing the neighbor vertices for each vertex. This function creates an igraph graph object from such a list.

Usage

graph.adjlist(adjlist, directed = TRUE, duplicate = TRUE)

Arguments

adjlist The adjacency list. It should be consistent, i.e. the maximum throughout all vectors in the list must be less than the number of vectors (=the number of vertices in the graph). Note that the list is expected to be 0-indexed.
directed Logical scalar, whether or not to create a directed graph.
duplicate Logical scalar. For undirected graphs it gives whether edges are included in the list twice. E.g. if it is TRUE then for an undirected {A,B} edge graph.adjlist expects A included in the neighbors of B and B to be included in the neighbors of A.
This argument is ignored if directed is TRUE.

Details

Adjacency lists are handy if you intend to do many (small) modifications to a graph. In this case adjacency lists are more efficient than igraph graphs.

The idea is that you convert your graph to an adjacency list by get.adjlist, do your modifications to the graphs and finally create again an igraph graph by calling graph.adjlist.

Value

An igraph graph object.

Author(s)

Gabor Csardi csardi@rmki.kfki.hu

See Also

get.edgelist

Examples

## Directed
g <- graph.ring(10, dir=TRUE)
al <- get.adjlist(g, mode="out")
g2 <- graph.adjlist(al)
graph.isomorphic(g, g2)

## Undirected
g <- graph.ring(10)
al <- get.adjlist(g)
g2 <- graph.adjlist(al, dir=FALSE)
graph.isomorphic(g, g2)
ecount(g2)
g3 <- graph.adjlist(al, dir=FALSE, duplicate=FALSE)
ecount(g3)
is.multiple(g3)

[Package igraph version 0.5.2 Index]