# E

0th

Percentile

##### Edges of a graph

An edge sequence is a vector containing numeric edge ids, with a special class attribute that allows custom operations: selecting subsets of edges based on attributes, or graph structure, creating the intersection, union of edges, etc.

##### Usage
E(graph, P = NULL, path = NULL, directed = TRUE)
##### Arguments
graph

The graph.

P

A list of vertices to select edges via pairs of vertices. The first and second vertices select the first edge, the third and fourth the second, etc.

path

A list of vertices, to select edges along a path. Note that this only works reliable for simple graphs. If the graph has multiple edges, one of them will be chosen arbitrarily to be included in the edge sequence.

directed

Whether to consider edge directions in the P argument, for directed graphs.

##### Details

Edge sequences are usually used as igraph function arguments that refer to edges of a graph.

An edge sequence is tied to the graph it refers to: it really denoted the specific edges of that graph, and cannot be used together with another graph.

An edge sequence is most often created by the E() function. The result includes edges in increasing edge id order by default (if. none of the P and path arguments are used). An edge sequence can be indexed by a numeric vector, just like a regular R vector. See links to other edge sequence operations below.

##### Value

An edge sequence of the graph.

##### Indexing edge sequences

Edge sequences mostly behave like regular vectors, but there are some additional indexing operations that are specific for them; e.g. selecting edges based on graph structure, or based on edge attributes. See [.igraph.es for details.

• E
##### Examples
# NOT RUN {
# Edges of an unnamed graph
g <- make_ring(10)
E(g)

# Edges of a named graph
g2 <- make_ring(10) %>%
set_vertex_attr("name", value = letters[1:10])
E(g2)
# }

Documentation reproduced from package igraph, version 1.0.1, License: GPL (>= 2)

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