# unfold.tree

0th

Percentile

##### 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
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:
• treeThe result, an igraph object, a tree or a forest.
• vertex_indexA numeric vector, it gives a mapping from the vertices of the new graph to the vertices of the old graph.

##### concept

• Tree
• Forest
g <- graph.tree(10)V(g)$id <- seq_len(vcount(g))-1 roots <- sapply(decompose.graph(g), function(x) { V(x)$id[ topological.sort(x)[1]+1 ] })
tree <- unfold.tree(g, roots=roots)