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A loop edge is an edge from a vertex to itself. An edge is a multiple edge if it has exactly the same head and tail vertices as another edge. A graph without multiple and loop edges is called a simple graph.

Usage

which_multiple(graph, eids = E(graph))

any_multiple(graph)

count_multiple(graph, eids = E(graph))

which_loop(graph, eids = E(graph))

any_loop(graph)

Arguments

graph

The input graph.

eids

The edges to which the query is restricted. By default this is all edges in the graph.

Value

any_loop() and any_multiple() return a logical scalar. which_loop() and which_multiple() return a logical vector. count_multiple() returns a numeric vector.

Details

any_loop() decides whether the graph has any loop edges.

which_loop() decides whether the edges of the graph are loop edges.

any_multiple() decides whether the graph has any multiple edges.

which_multiple() decides whether the edges of the graph are multiple edges.

count_multiple() counts the multiplicity of each edge of a graph.

Note that the semantics for which_multiple() and count_multiple() is different. which_multiple() gives TRUE for all occurrences of a multiple edge except for one. I.e. if there are three i-j edges in the graph then which_multiple() returns TRUE for only two of them while count_multiple() returns ‘3’ for all three.

See the examples for getting rid of multiple edges while keeping their original multiplicity as an edge attribute.

See also

Author

Gabor Csardi csardi.gabor@gmail.com

Examples


# Loops
g <- make_graph(c(1, 1, 2, 2, 3, 3, 4, 5))
any_loop(g)
#> [1] TRUE
which_loop(g)
#> [1]  TRUE  TRUE  TRUE FALSE

# Multiple edges
g <- sample_pa(10, m = 3, algorithm = "bag")
any_multiple(g)
#> [1] TRUE
which_multiple(g)
#>  [1] FALSE  TRUE  TRUE FALSE  TRUE  TRUE FALSE FALSE  TRUE FALSE  TRUE  TRUE
#> [13] FALSE FALSE  TRUE FALSE FALSE FALSE FALSE  TRUE  TRUE FALSE FALSE  TRUE
#> [25] FALSE FALSE FALSE
count_multiple(g)
#>  [1] 3 3 3 3 3 3 1 2 2 3 3 3 2 1 2 1 1 1 3 3 3 2 1 2 1 1 1
which_multiple(simplify(g))
#>  [1] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
#> [13] FALSE FALSE FALSE FALSE
all(count_multiple(simplify(g)) == 1)
#> [1] TRUE

# Direction of the edge is important
which_multiple(make_graph(c(1, 2, 2, 1)))
#> [1] FALSE FALSE
which_multiple(make_graph(c(1, 2, 2, 1), dir = FALSE))
#> [1] FALSE  TRUE

# Remove multiple edges but keep multiplicity
g <- sample_pa(10, m = 3, algorithm = "bag")
E(g)$weight <- count_multiple(g)
g <- simplify(g, edge.attr.comb = list(weight = "min"))
any(which_multiple(g))
#> [1] FALSE
E(g)$weight
#>  [1] 3 2 1 2 1 3 3 3 2 1 1 1 1 2 1