Find One Total Order Consistent with Partial Order or With Directed
Acyclic Graph
Usage
tsort(from, to, domain, strict = TRUE)
Arguments
from
an atomic vector
to
an atomic vector of the same mode and length as from
domain
an atomic vector of the same mode as from containing
all the elements of from and to. If missing,
union(from, to) is used. The domain of the relation or the
nodes of the graph.
strict
logical. If TRUE then from[i] == to[i] is
an error. Otherwise, such edges of the graph are ignored.
Value
A vector that is a reordering of domain so that every element of
from appears in the value before the corresponding element of to.Throws an error if there is no consistent total order (the graph has a cycle).
Details
Pairs (from[i], to[i]) can be though of either as elements of
a relation on a set or as edges in a directed graph.
This function finds one total order on the domain (nodes of the graph)
that is consistent with the relation (graph) if one exists (that is if the
graph is directed).