# 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)
# }
```

*Documentation reproduced from package igraph, version 1.0.1, License: GPL (>= 2)*