R igraph manual pages

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 is a (v1, v2) exists in the graph.

See Also

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

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