unfold_tree
Convert a general graph into a forest
Perform a breadth-first search on a graph and convert it into a tree or forest by replicating vertices that were found more than once.
- Keywords
- graphs
Usage
unfold_tree(graph, mode = c("all", "out", "in", "total"), roots)Arguments
- graph
The input graph, it can be either directed or undirected.
- mode
Character string, defined the types of the paths used for the breadth-first search. “out” follows the outgoing, “in” the incoming edges, “all” and “total” both of them. This argument is ignored for undirected graphs.
- roots
A vector giving the vertices from which the breadth-first search is performed. Typically it contains one vertex per component.
Details
A forest is a graph, whose components are trees.
The roots vector can be calculated by simply doing a topological sort
in all components of the graph, see the examples below.
Value
A list with two components:
The result, an igraph
object, a tree or a forest.
A numeric vector, it gives a mapping from the vertices of the new graph to the vertices of the old graph.
Examples
# NOT RUN {
g <- make_tree(10) %du% make_tree(10)
V(g)$id <- seq_len(vcount(g))-1
roots <- sapply(decompose(g), function(x) {
V(x)$id[ topo_sort(x)[1]+1 ] })
tree <- unfold_tree(g, roots=roots)
# }