Find mutual edges in a directed graph

This function checks the reciprocal pair of the supplied edges.

which_mutual(graph, eids = E(graph), loops = TRUE)

Arguments

graph

The input graph.

eids

Edge sequence, the edges that will be probed. By default is includes all edges in the order of their ids.

loops

Logical, whether to consider directed self-loops to be mutual.

Value

A logical vector of the same length as the number of edges supplied.

Details

In a directed graph an (A,B) edge is mutual if the graph also includes a (B,A) directed edge.

Note that multi-graphs are not handled properly, i.e. if the graph contains two copies of (A,B) and one copy of (B,A), then these three edges are considered to be mutual.

Undirected graphs contain only mutual edges by definition.

See also

reciprocity(), dyad_census() if you just want some statistics about mutual edges.

Other structural.properties: bfs(), component_distribution(), connect(), constraint(), coreness(), degree(), dfs(), distance_table(), edge_density(), feedback_arc_set(), girth(), is_acyclic(), is_dag(), is_matching(), k_shortest_paths(), knn(), reciprocity(), subcomponent(), subgraph(), topo_sort(), transitivity(), unfold_tree(), which_multiple()

Author

Gabor Csardi csardi.gabor@gmail.com

Related documentation in the C library

igraph_is_mutual().

Examples

g <- sample_gnm(10, 50, directed = TRUE)
reciprocity(g)
#> [1] 0.52
dyad_census(g)
#> $mut
#> [1] 13
#> 
#> $asym
#> [1] 24
#> 
#> $null
#> [1] 8
#> 
which_mutual(g)
#>  [1] FALSE  TRUE FALSE  TRUE  TRUE  TRUE FALSE FALSE  TRUE  TRUE  TRUE FALSE
#> [13]  TRUE  TRUE FALSE FALSE  TRUE FALSE  TRUE  TRUE FALSE  TRUE FALSE FALSE
#> [25] FALSE FALSE  TRUE  TRUE FALSE FALSE FALSE  TRUE FALSE  TRUE FALSE FALSE
#> [37] FALSE  TRUE  TRUE FALSE FALSE  TRUE FALSE  TRUE  TRUE FALSE  TRUE  TRUE
#> [49]  TRUE  TRUE
sum(which_mutual(g)) / 2 == dyad_census(g)$mut
#> [1] TRUE