# is.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
is.loop(graph, eids=E(graph))
is.multiple(graph, eids=E(graph))
count.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

Note that the semantics for is.multiple and count.multiple is different. is.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 is.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

• is.loop and is.multiple return a logical vector. count.multiple returns a numeric vector.

##### concept

Simple graph

simplify to eliminate loop and multiple edges.

##### Aliases
• is.loop
• is.multiple
• count.multiple
##### Examples
# Loops
g <- graph( c(0,0,1,1,2,2,3,4) )
is.loop(g)

# Multiple edges
g <- barabasi.game(10, m=3)
is.multiple(g)
count.multiple(g)
is.multiple(simplify(g))
all(count.multiple(simplify(g)) == 1)

# Direction of the edge is important
is.multiple(graph( c(0,1, 1,0) ))
is.multiple(graph( c(0,1, 1,0), dir=FALSE ))

# Remove multiple edges but keep multiplicity
g <- barabasi.game(10, m=3)
E(g)$weight <- count.multiple(g) g <- simplify(g) any(is.multiple(g)) E(g)$weight
Documentation reproduced from package igraph, version 0.5.5-3, License: GPL (>= 2)

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