Skip to contents

Neighborhood of graph vertices

Source: R/games.R, R/structural-properties.R
ego.Rd

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. Negative values indicate an infinite order.

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.

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.

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.

connect_neighborhood(), vcount()

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(), transitive_closure(), union(), union.igraph(), vertex()

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

Author

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)
#> [1] 1 1 1
ego_size(g, order = 1, 1:3)
#> [1] 3 3 3
ego_size(g, order = 2, 1:3)
#> [1] 5 5 5

# neighborhood_size() is an alias of ego_size()
neighborhood_size(g, order = 0, 1:3)
#> [1] 1 1 1
neighborhood_size(g, order = 1, 1:3)
#> [1] 3 3 3
neighborhood_size(g, order = 2, 1:3)
#> [1] 5 5 5

ego(g, order = 0, 1:3)
#> [[1]]
#> + 1/10 vertex, from 69a1619:
#> [1] 1
#> 
#> [[2]]
#> + 1/10 vertex, from 69a1619:
#> [1] 2
#> 
#> [[3]]
#> + 1/10 vertex, from 69a1619:
#> [1] 3
#> 
ego(g, order = 1, 1:3)
#> [[1]]
#> + 3/10 vertices, from 69a1619:
#> [1]  1  2 10
#> 
#> [[2]]
#> + 3/10 vertices, from 69a1619:
#> [1] 2 1 3
#> 
#> [[3]]
#> + 3/10 vertices, from 69a1619:
#> [1] 3 2 4
#> 
ego(g, order = 2, 1:3)
#> [[1]]
#> + 5/10 vertices, from 69a1619:
#> [1]  1  2 10  3  9
#> 
#> [[2]]
#> + 5/10 vertices, from 69a1619:
#> [1]  2  1  3 10  4
#> 
#> [[3]]
#> + 5/10 vertices, from 69a1619:
#> [1] 3 2 4 1 5
#> 

# neighborhood() is an alias of ego()
neighborhood(g, order = 0, 1:3)
#> [[1]]
#> + 1/10 vertex, from 69a1619:
#> [1] 1
#> 
#> [[2]]
#> + 1/10 vertex, from 69a1619:
#> [1] 2
#> 
#> [[3]]
#> + 1/10 vertex, from 69a1619:
#> [1] 3
#> 
neighborhood(g, order = 1, 1:3)
#> [[1]]
#> + 3/10 vertices, from 69a1619:
#> [1]  1  2 10
#> 
#> [[2]]
#> + 3/10 vertices, from 69a1619:
#> [1] 2 1 3
#> 
#> [[3]]
#> + 3/10 vertices, from 69a1619:
#> [1] 3 2 4
#> 
neighborhood(g, order = 2, 1:3)
#> [[1]]
#> + 5/10 vertices, from 69a1619:
#> [1]  1  2 10  3  9
#> 
#> [[2]]
#> + 5/10 vertices, from 69a1619:
#> [1]  2  1  3 10  4
#> 
#> [[3]]
#> + 5/10 vertices, from 69a1619:
#> [1] 3 2 4 1 5
#> 

# 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)
#> [[1]]
#> IGRAPH acaba98 UN-- 5 4 -- Ring graph
#> + attr: name (g/c), mutual (g/l), circular (g/l), name (v/c)
#> + edges from acaba98 (vertex names):
#> [1] a--b b--c a--j i--j
#> 
#> [[2]]
#> IGRAPH 418a302 UN-- 5 4 -- Ring graph
#> + attr: name (g/c), mutual (g/l), circular (g/l), name (v/c)
#> + edges from 418a302 (vertex names):
#> [1] a--b b--c c--d a--j
#> 
#> [[3]]
#> IGRAPH a91f848 UN-- 5 4 -- Ring graph
#> + attr: name (g/c), mutual (g/l), circular (g/l), name (v/c)
#> + edges from a91f848 (vertex names):
#> [1] a--b b--c c--d d--e
#> 
# make_neighborhood_graph() is an alias of make_ego_graph()
make_neighborhood_graph(g, order = 2, 1:3)
#> [[1]]
#> IGRAPH a6f1679 UN-- 5 4 -- Ring graph
#> + attr: name (g/c), mutual (g/l), circular (g/l), name (v/c)
#> + edges from a6f1679 (vertex names):
#> [1] a--b b--c a--j i--j
#> 
#> [[2]]
#> IGRAPH 8144b15 UN-- 5 4 -- Ring graph
#> + attr: name (g/c), mutual (g/l), circular (g/l), name (v/c)
#> + edges from 8144b15 (vertex names):
#> [1] a--b b--c c--d a--j
#> 
#> [[3]]
#> IGRAPH 30ab8ff UN-- 5 4 -- Ring graph
#> + attr: name (g/c), mutual (g/l), circular (g/l), name (v/c)
#> + edges from 30ab8ff (vertex names):
#> [1] a--b b--c c--d d--e
#> 

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