are_adjacent {igraph}

Are two vertices adjacent?

Description

The order of the vertices only matters in directed graphs, where the existence of a directed ⁠(v1, v2)⁠ edge is queried.

Usage

are_adjacent(graph, v1, v2)

Arguments

graph

The graph.

v1

The first vertex, tail in directed graphs.

v2

The second vertex, head in directed graphs.

Value

A logical scalar, TRUE if edge ⁠(v1, v2)⁠ exists in the graph.

See Also

Other structural queries: [.igraph(), [[.igraph(), adjacent_vertices(), ends(), get.edge.ids(), gorder(), gsize(), head_of(), incident(), incident_edges(), is_directed(), neighbors(), tail_of()

Examples

ug <- make_ring(10)
ug
are_adjacent(ug, 1, 2)
are_adjacent(ug, 2, 1)

dg <- make_ring(10, directed = TRUE)
dg
are_adjacent(ug, 1, 2)
are_adjacent(ug, 2, 1)