separates: A function to test whether a subset of nodes separates
two other subsets of nodes.
Description
The function tests to see whether a set of nodes, S1, separates
all nodes in a from all nodes in b.
Usage
separates(a, b, S1, g)
Arguments
a
The names of the nodes in the from set.
b
The names of the nodes in the to set.
S1
The names of the nodes in the separation set.
g
An instance of the graph class. All nodes
named in the other arguments must be nodes of this graph.
Value
Either TRUE or FALSE depending on whether S1 separates
a from b in g1.
Details
The algorithm is quite simple. A subgraph is created by removing the
nodes named in S1 from g. Then all paths between
elements of a to elements of b are tested for. If any
path exists the function returns FALSE, otherwise it returns
TRUE.