subgraph {igraph}

Subgraph of a graph

Description

subgraph() creates a subgraph of a graph, containing only the specified vertices and all the edges among them.

Usage

subgraph(graph, vids)

induced_subgraph(
  graph,
  vids,
  impl = c("auto", "copy_and_delete", "create_from_scratch")
)

subgraph.edges(graph, eids, delete.vertices = TRUE)

Arguments

graph

The original graph.

vids

Numeric vector, the vertices of the original graph which will form the subgraph.

impl

Character scalar, to choose between two implementation of the subgraph calculation. ‘copy_and_delete’ copies the graph first, and then deletes the vertices and edges that are not included in the result graph. ‘create_from_scratch’ searches for all vertices and edges that must be kept and then uses them to create the graph from scratch. ‘auto’ chooses between the two implementations automatically, using heuristics based on the size of the original and the result graph.

eids

The edge ids of the edges that will be kept in the result graph.

delete.vertices

Logical scalar, whether to remove vertices that do not have any adjacent edges in eids.

Details

induced_subgraph() calculates the induced subgraph of a set of vertices in a graph. This means that exactly the specified vertices and all the edges between them will be kept in the result graph.

subgraph.edges() calculates the subgraph of a graph. For this function one can specify the vertices and edges to keep. This function will be renamed to subgraph() in the next major version of igraph.

The subgraph() function currently does the same as induced_subgraph() (assuming ‘auto’ as the impl argument), but this behaviour is deprecated. In the next major version, subgraph() will overtake the functionality of subgraph.edges().

Value

A new graph object.

Author(s)

Gabor Csardi [e-mail]

See Also

Other structural.properties: bfs(), component_distribution(), connect(), constraint(), coreness(), degree(), dfs(), distance_table(), edge_density(), feedback_arc_set(), girth(), is_acyclic(), is_dag(), is_matching(), k_shortest_paths(), knn(), reciprocity(), subcomponent(), topo_sort(), transitivity(), unfold_tree(), which_multiple(), which_mutual()

Examples

g <- make_ring(10)
g2 <- induced_subgraph(g, 1:7)
g3 <- subgraph.edges(g, 1:5)