conversion

0th

Percentile

Convert a graph to an adjacency matrix or an edge list

Sometimes it is useful to have a standard representation of a graph, like an adjacency matrix or an edge list.

Keywords
graphs
Usage
get.adjacency(graph, type=c("both", "upper", "lower"),
       attr=NULL, edges=FALSE, names=TRUE,
       sparse=getIgraphOpt("sparsematrices"))
get.edgelist(graph, names=TRUE)
Arguments
graph
The graph to convert.
type
Gives how to create the adjacency matrix for undirected graphs. It is ignored for directed graphs. Possible values: upper: the upper right triangle of the matrix is used, lower: the lower left triangle of the matrix i
attr
Either NULL or a character string giving an edge attribute name. If NULL a traditional adjacency matrix is returned. If not NULL then the values of the given edge attribute are included in the adjacency m
edges
Logical scalar, whether to return the edge ids in the matrix. For non-existant edges zero is returned.
names
Logical constant.

For graph.adjacenct it gives whether to assign row and column names to the matrix. These are only assigned if the name vertex attribute is present in the graph.

for get.edgelist it

sparse
Logical scalar, whether to create a sparse matrix. The Matrix package must be installed for creating sparse matrices.
Details

get.adjacency returns the adjacency matrix of a graph, a regular Rmatrix if sparse is FALSE, or a sparse matrix, as defined in the Matrix package, if sparse if TRUE. get.edgelist returns the list of edges in a graph.

Value

  • A vcount(graph) by vcount(graph) (usually) numeric matrix for get.adjacency. (This can be huge!) Note that a non-numeric matrix might be returned if attr is a non-numeric edge attribute.

    A ecount(graph) by 2 numeric matrix for get.edgelist.

concept

  • Edge list
  • Adjacency list

See Also

graph.adjacency, read.graph

Aliases
  • get.adjacency
  • get.edgelist
Examples
g <- erdos.renyi.game(10, 2/10)
get.edgelist(g)
get.adjacency(g)
V(g)$name <- letters[1:vcount(g)]
get.adjacency(g)
E(g)$weight <- runif(ecount(g))
get.adjacency(g, attr="weight")
Documentation reproduced from package igraph, version 0.7.1, License: GPL (>= 2)

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