Returns the Boundary between a Graph and a SubGraph
The boundary of a subgraph is the set of nodes in the original graph
that have edges to nodes in the subgraph. The function
computes the boundary and returns it as a list whose length is the same
length as the number of nodes in the subgraph.
- the original graph from which the boundary will be created
- can either be the vector of the node labels or the subgraph itself.
The boundary of a subgraph is the set of nodes in the graph which have an edge that connects them to the specified subgraph but which are themselves not elements of the subgraph.
For convenience users can specify the subgraph as either a graph or a vector of node labels.
This function returns a named list of length equal to the number of
subgraph. The elements of the list correspond to the nodes in the
subgraph. The elements are lists of the nodes in
graphwhich share an edge with the respective node in
set.seed(123) g1 <- randomGraph(letters[1:10], 1:4, p=.3) ##both should be "a" boundary(c("g", "i"), g1)