# which_multiple

0th

Percentile

##### Find the multiple or loop edges in a graph

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.

Keywords
graphs
##### Usage
which_multiple(graph, eids = E(graph))
##### Arguments
graph

The input graph.

eids

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

##### Details

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 occurences of a multiple edge except for one. Ie. 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.

##### Value

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

simplify to eliminate loop and multiple edges.

##### Aliases
• which_multiple
• has.multiple
• is.loop
• is.multiple
• count.multiple
• count_multiple
• any_multiple
• which_loop
##### Examples
# NOT RUN {
# Loops
g <- graph( c(1,1,2,2,3,3,4,5) )
which_loop(g)

# Multiple edges
g <- barabasi.game(10, m=3, algorithm="bag")
any_multiple(g)
which_multiple(g)
count_multiple(g)
which_multiple(simplify(g))
all(count_multiple(simplify(g)) == 1)

# Direction of the edge is important
which_multiple(graph( c(1,2, 2,1) ))
which_multiple(graph( c(1,2, 2,1), dir=FALSE ))

# Remove multiple edges but keep multiplicity
g <- barabasi.game(10, m=3, algorithm="bag")
E(g)$weight <- count_multiple(g) g <- simplify(g) any(which_multiple(g)) E(g)$weight

# }

Documentation reproduced from package igraph, version 1.2.3, License: GPL (>= 2)

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