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.
which_multiple(graph, eids = E(graph))
graph |
The input graph. |
eids |
The edges to which the query is restricted. By default this is all edges in the graph. |
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. 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.
any_multiple returns a logical scalar. which_loop and
which_multiple return a logical vector. count_multiple returns a
numeric vector.
Gabor Csardi csardi.gabor@gmail.com
simplify to eliminate loop and multiple edges.
# 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
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