KEGGgraph (version 1.30.0)

neighborhood: Return the neighborhood set of given vertices

Description

The function returns the neighborhood set of given vertices in the form of list. Optionally user can choose to include the given vertices in the list, too.

Usage

neighborhood(graph, index, return.self = FALSE)

Arguments

graph

An object of graphNEL

index

Names of nodes, whose neighborhood set should be returned

return.self

logical, should the vertex itself also be returned?

Value

A list indexed by the given node indices, each entry containing the neighborhood set of that node (or furthermore including that node).

Details

Let v be a vertex in a (di)graph, the out-neighborhood or successor set (N+(v), x belongs to V(G) and v->x) and the in-neighborhood or predecessor set (N-(v), x belongs to V(G) and x->v) are jointly returned.

The returned list is indexed by the given node indices, NULL is returned in case of non-existing node.

The nodes are unique, that is, duplicated nodes are removed in results.

References

D.B. West. Introduction to Graph Theory, Second Edition. Prentice Hall, 2001

Examples

  V <- c("Hamburg","Stuttgart","Berlin","Paris","Bremen")
  E <- list("Hamburg"=c("Berlin","Bremen"),
            "Stuttgart"=c("Berlin","Paris"),
            "Berlin"=c("Stuttgart","Bremen"),
            "Paris"=c("Stuttgart"),
            "Bremen"=c("Hamburg","Berlin"))
  g <- new("graphNEL", nodes=V, edgeL=E, edgemode="directed")
  if(require(Rgraphviz) & interactive()) {
    plot(g, "neato")
  }

  ## simple uses
  neighborhood(g, "Hamburg")
  neighborhood(g, c("Hamburg", "Berlin","Paris"))

  ## in case of non-existing nodes
  neighborhood(g, c("Stuttgart","Ulm"))

  ## also applicable to non-directed graphs
  neighborhood(ugraph(g), c("Stuttgart","Berlin"))