bfs {igraph} | R Documentation |
Breadth-first search
Description
Breadth-first search is an algorithm to traverse a graph. We start from a root vertex and spread along every edge “simultaneously”.
Usage
bfs(
graph,
root,
mode = c("out", "in", "all", "total"),
unreachable = TRUE,
restricted = NULL,
order = TRUE,
rank = FALSE,
father = FALSE,
pred = FALSE,
succ = FALSE,
dist = FALSE,
callback = NULL,
extra = NULL,
rho = parent.frame(),
neimode
)
Arguments
graph |
The input graph. |
root |
Numeric vector, usually of length one. The root vertex, or root vertices to start the search from. |
mode |
For directed graphs specifies the type of edges to follow. ‘out’ follows outgoing, ‘in’ incoming edges. ‘all’ ignores edge directions completely. ‘total’ is a synonym for ‘all’. This argument is ignored for undirected graphs. |
unreachable |
Logical scalar, whether the search should visit the
vertices that are unreachable from the given root vertex (or vertices). If
|
restricted |
|
order |
Logical scalar, whether to return the ordering of the vertices. |
rank |
Logical scalar, whether to return the rank of the vertices. |
father |
Logical scalar, whether to return the father of the vertices. |
pred |
Logical scalar, whether to return the predecessors of the vertices. |
succ |
Logical scalar, whether to return the successors of the vertices. |
dist |
Logical scalar, whether to return the distance from the root of the search tree. |
callback |
If not |
extra |
Additional argument to supply to the callback function. |
rho |
The environment in which the callback function is evaluated. |
neimode |
This argument is deprecated from igraph 1.3.0; use
|
Details
The callback function must have the following arguments:
- graph
The input graph is passed to the callback function here.
- data
A named numeric vector, with the following entries: ‘vid’, the vertex that was just visited, ‘pred’, its predecessor (zero if this is the first vertex), ‘succ’, its successor (zero if this is the last vertex), ‘rank’, the rank of the current vertex, ‘dist’, its distance from the root of the search tree.
- extra
The extra argument.
The callback must return FALSE
to continue the search or TRUE
to terminate it. See examples below on how to
use the callback function.
Value
A named list with the following entries:
root |
Numeric scalar. The root vertex that was used as the starting point of the search. |
neimode |
Character scalar. The |
order |
Numeric vector. The vertex ids, in the order in which they were visited by the search. |
rank |
Numeric vector. The rank for each vertex, zero for unreachable vertices. |
father |
Numeric vector. The father of each vertex, i.e. the vertex it was discovered from. |
pred |
Numeric vector. The previously visited vertex for each vertex, or 0 if there was no such vertex. |
succ |
Numeric vector. The next vertex that was visited after the current one, or 0 if there was no such vertex. |
dist |
Numeric vector, for each vertex its distance from the
root of the search tree. Unreachable vertices have a negative distance
as of igraph 1.6.0, this used to be |
Note that order
, rank
, father
, pred
, succ
and dist
might be NULL
if their corresponding argument is
FALSE
, i.e. if their calculation is not requested.
Author(s)
Gabor Csardi csardi.gabor@gmail.com
See Also
dfs()
for depth-first search.
Other structural.properties:
component_distribution()
,
connect()
,
constraint()
,
coreness()
,
degree()
,
dfs()
,
distance_table()
,
edge_density()
,
feedback_arc_set()
,
girth()
,
is_acyclic()
,
is_dag()
,
is_matching()
,
k_shortest_paths()
,
knn()
,
reciprocity()
,
subcomponent()
,
subgraph()
,
topo_sort()
,
transitivity()
,
unfold_tree()
,
which_multiple()
,
which_mutual()
Examples
## Two rings
bfs(make_ring(10) %du% make_ring(10),
root = 1, "out",
order = TRUE, rank = TRUE, father = TRUE, pred = TRUE,
succ = TRUE, dist = TRUE
)
## How to use a callback
f <- function(graph, data, extra) {
print(data)
FALSE
}
tmp <- bfs(make_ring(10) %du% make_ring(10),
root = 1, "out",
callback = f
)
## How to use a callback to stop the search
## We stop after visiting all vertices in the initial component
f <- function(graph, data, extra) {
data["succ"] == -1
}
bfs(make_ring(10) %du% make_ring(10), root = 1, callback = f)