Use this if you are using igraph from R
Breadth-first search is an algorithm to traverse a graph. We start from a root vertex and spread along every edge “simultaneously”.
bfs(graph, root, neimode = 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())
graph |
The input graph. |
root |
Numeric vector, usually of length one. The root vertex, or root vertices to start the search from. |
neimode |
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. |
The callback function must have the following arguments:
The input graph is passed to the callback function here.
A named numeric vector, with the following entries: ‘vid’, the vertex that was just visited, ‘pred’, its predecessor, ‘succ’, its successor, ‘rank’, the rank of the current vertex, ‘dist’, its distance from the root of the search tree.
The extra argument.
See examples below on how to use the callback function.
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. |
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. |
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.
Gabor Csardi csardi.gabor@gmail.com
dfs
for depth-first search.
## 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)