R igraph manual pages

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.

Usage

ego_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)

make_ego_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.
nodes	The vertices for which the calculation is performed.
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.
mindist	The minimum distance to include the vertex in the result.

Details

The neighborhood of a given order o of a vertex v includes all vertices which are closer to v than the order. Ie. 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 calculates the size of the neighborhoods for the given vertices with the given order.

ego calculates the neighborhoods of the given vertices with the given order parameter.

make_ego_graph 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 returns with an integer vector.

ego returns with a list of integer vectors.

make_ego_graph returns with a list of graphs.

connect returns with a new graph object.

Author(s)

Gabor Csardi csardi.gabor@gmail.com, the first version was done by Vincent Matossian

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

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

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