igraph (version 0.7.1)

structure.info: Gaining information about graph structure

Description

Functions for exploring the basic structure of a network: number of vertices and edges, the neighbors of a node, test whether two vertices are connected by an edge.

Usage

vcount(graph)
ecount(graph)
neighbors(graph, v, mode = 1)
incident(graph, v, mode=c("all", "out", "in", "total"))
is.directed(graph)
are.connected(graph, v1, v2)
get.edge(graph, id)
get.edges(graph, es)

Arguments

graph

The graph.

v

The vertex of which the adjacent vertices or incident edges are queried.

mode

Character string, specifying the type of adjacent vertices or incident edges to list in a directed graph. If out, then only outgoing edges (or their corresponding vertices) are considered; in considers incomin

v1

The id of the first vertex. For directed graphs only edges pointing from v1 to v2 are searched.

v2

The id of the second vertex. For directed graphs only edges pointing from v1 to v2 are searched.

id

A numeric edge id.

es

An edge sequence.

Value

• vcount and ecount return integer constants. neighbors returns an integer vector. is.directed and are.connected return boolean constants. get.edge returns a numeric vector of length two. get.edges returns a two-column matrix.

Details

These functions provide the basic structural information of a graph.

vcount gives the number of vertices in the graph.

ecount gives the number of edges in the graph.

neighbors gives the neighbors of a vertex. The vertices connected by multiple edges are listed as many times as the number of connecting edges.

incident gives the incident edges of a vertex. is.directed gives whether the graph is directed or not. It just gives its directed attribute. are.connected decides whether there is an edge from v1 to v2.

get.edge returns the end points of the edge with the supplied edge id. For directed graph the source vertex comes first, for undirected graphs, the order is arbitrary.

get.edges returns a matrix with the endpoints of the edges in the edge sequence argument.

See Also

graph

Examples

g <- graph.ring(10)
vcount(g)
ecount(g)
neighbors(g, 5)
incident(g, 5)
are.connected(g, 1, 2)
are.connected(g, 2, 4)
get.edges(g, 1:6)