connect {igraph}

Neighborhood of graph vertices

Description

These functions find the vertices not farther than a given limit from another fixed vertex, these are called the neighborhood of the vertex. Note that ego() and neighborhood(), ego_size() and neighborhood_size(), make_ego_graph() and ⁠make_neighborhood()_graph()⁠, are synonyms (aliases).

Usage

connect(graph, order, mode = c("all", "out", "in", "total"))

ego_size(
  graph,
  order = 1,
  nodes = V(graph),
  mode = c("all", "out", "in"),
  mindist = 0
)

neighborhood_size(
  graph,
  order = 1,
  nodes = V(graph),
  mode = c("all", "out", "in"),
  mindist = 0
)

ego(
  graph,
  order = 1,
  nodes = V(graph),
  mode = c("all", "out", "in"),
  mindist = 0
)

neighborhood(
  graph,
  order = 1,
  nodes = V(graph),
  mode = c("all", "out", "in"),
  mindist = 0
)

make_ego_graph(
  graph,
  order = 1,
  nodes = V(graph),
  mode = c("all", "out", "in"),
  mindist = 0
)

make_neighborhood_graph(
  graph,
  order = 1,
  nodes = V(graph),
  mode = c("all", "out", "in"),
  mindist = 0
)

Arguments

graph

The input graph.

order

Integer giving the order of the neighborhood.

mode

Character constant, it specifies how to use the direction of the edges if a directed graph is analyzed. For ‘out’ only the outgoing edges are followed, so all vertices reachable from the source vertex in at most order steps are counted. For ‘"in"’ all vertices from which the source vertex is reachable in at most order steps are counted. ‘"all"’ ignores the direction of the edges. This argument is ignored for undirected graphs.

nodes

The vertices for which the calculation is performed.

mindist

The minimum distance to include the vertex in the result.

Details

The neighborhood of a given order r of a vertex v includes all vertices which are closer to v than the order. I.e. order 0 is always v itself, order 1 is v plus its immediate neighbors, order 2 is order 1 plus the immediate neighbors of the vertices in order 1, etc.

ego_size()/neighborhood_size() (synonyms) returns the size of the neighborhoods of the given order, for each given vertex.

ego()/neighborhood() (synonyms) returns the vertices belonging to the neighborhoods of the given order, for each given vertex.

make_ego_graph()/⁠make_neighborhood()_graph()⁠ (synonyms) is creates (sub)graphs from all neighborhoods of the given vertices with the given order parameter. This function preserves the vertex, edge and graph attributes.

connect() creates a new graph by connecting each vertex to all other vertices in its neighborhood.

Value

• ego_size()/neighborhood_size() returns with an integer vector.

• ego()/neighborhood() (synonyms) returns A list of igraph.vs or a list of numeric vectors depending on the value of igraph_opt("return.vs.es"), see details for performance characteristics.

• make_ego_graph()/make_neighborhood_graph() returns with a list of graphs.

• connect() returns with a new graph object.

Author(s)

Gabor Csardi [e-mail], the first version was done by Vincent Matossian

See Also

Other functions for manipulating graph structure: +.igraph(), add_edges(), add_vertices(), complementer(), compose(), contract(), delete_edges(), delete_vertices(), difference(), difference.igraph(), disjoint_union(), edge(), igraph-minus, intersection(), intersection.igraph(), path(), permute(), rep.igraph(), reverse_edges(), simplify(), union(), union.igraph(), vertex()

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

Examples

g <- make_ring(10)

ego_size(g, order = 0, 1:3)
ego_size(g, order = 1, 1:3)
ego_size(g, order = 2, 1:3)

# neighborhood_size() is an alias of ego_size()
neighborhood_size(g, order = 0, 1:3)
neighborhood_size(g, order = 1, 1:3)
neighborhood_size(g, order = 2, 1:3)

ego(g, order = 0, 1:3)
ego(g, order = 1, 1:3)
ego(g, order = 2, 1:3)

# neighborhood() is an alias of ego()
neighborhood(g, order = 0, 1:3)
neighborhood(g, order = 1, 1:3)
neighborhood(g, order = 2, 1:3)

# attributes are preserved
V(g)$name <- c("a", "b", "c", "d", "e", "f", "g", "h", "i", "j")
make_ego_graph(g, order = 2, 1:3)
# make_neighborhood_graph() is an alias of make_ego_graph()
make_neighborhood_graph(g, order = 2, 1:3)

# connecting to the neighborhood
g <- make_ring(10)
g <- connect(g, 2)