A {streamDAG}

Arcs of a directed graph

Description

This function and its documentation have been lifted from the igraph function E with arguments according to DAG conventions. An arc sequence is a vector containing numeric arc ids, with a special class attribute that allows custom operations: selecting subsets of arcs based on attributes, or graph structure, creating the intersection, union of arcs, etc.

Usage

A(G, P, path)

Arguments

G

Graph object of class igraph. See graph_from_literal.

P

A list of node to select arcs via pairs of nodes. The first and second nodes select the first arc, the third and fourth node select the second arc, etc.

path

A list of nodes, to select arcs along a path. Note that this only works reliably for simple graphs. If the graph has multiple arcs, one of them will be chosen arbitrarily to be included in the arc sequence.

Details

Arc sequences are usually used as function arguments that refer to arcs of a graph.

An arc sequence is tied to the graph it refers to: it really denoted the specific arcs of that graph, and cannot be used together with another graph.

An arc sequence is most often created by the A() function. The result includes arcs in increasing arc id order by default (if none of the P and path arguments are used). An arc sequence can be indexed by a numeric vector, just like a regular R vector.

Value

An arc sequence of the graph.

Author(s)

Gabor Csardi

See Also

See E

Examples

 G <- graph_from_literal(a --+ b, c --+ d, d --+ e, b --+ e, e --+ j, j --+ m, f --+ g, g --+ i, 
 h --+ i, i --+ k, k --+ l, l --+ m, m --+ n,  n --+ o)
 
A(G)