igraph (version 1.0.0)

ego: 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(graph, order, nodes = V(graph), mode = c("all", "out", "in"),
  mindist = 0)
make_ego_graph(graph, order, 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 constatnt, 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 ar

mindist

The minimum distance to include the vertex in the result.

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.

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.

Examples

g <- make_ring(10)
ego_size(g, 0, 1:3)
ego_size(g, 1, 1:3)
ego_size(g, 2, 1:3)
ego(g, 0, 1:3)
ego(g, 1, 1:3)
ego(g, 2, 1:3)

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

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