do_bfs: Use the breadth-first search (bfs) algorithm

In rich-iannone/DiagrammeR: Graph/Network Visualization

Use the breadth-first search (bfs) algorithm

Description

With a chosen or random node serving as the starting point, perform a breadth-first search of the whole graph and return the node ID values visited. The bfs algorithm differs from depth-first search (dfs) in that bfs will follow tree branches branches one level at a time until terminating at leaf node (dfs traverses branches as far as possible).

Usage

do_bfs(graph, node = NULL, direction = "all")

Arguments

graph	A graph object of class dgr_graph.
node	An optional node ID value to specify a single starting point for the bfs. If not provided, a random node from the graph will be chosen.
direction	Using all (the default), the bfs will ignore edge direction while traversing through the graph. With out and ⁠in⁠, traversals between adjacent nodes will respect the edge direction.

Value

A vector containing node ID values for nodes visited during the breadth-first search. The order of the node IDs corresponds to the order visited.

Examples

# Create a graph containing
# two balanced trees
graph <-
  create_graph() %>%
  add_balanced_tree(
    k = 2, h = 2) %>%
  add_balanced_tree(
    k = 3, h = 2)

# Perform a breadth-first
# search of the graph,
# beginning at the root node
# `1` (the default
# `direction = "all"` doesn't
# take edge direction into
# account)
graph %>%
  do_bfs(node = 1)

# If not specifying a
# starting node, the function
# will begin the search from
# a random node
graph %>%
  do_bfs()

# It's also possible to
# perform bfs while taking
# into account edge direction;
# using `direction = "in"`
# causes the bfs routine to
# visit nodes along inward edges
graph %>%
  do_bfs(
    node = 1,
    direction = "in")

# Using `direction = "out"`
# results in the bfs moving
# along solely outward edges
graph %>%
  do_bfs(
    node = 1,
    direction = "out")

rich-iannone/DiagrammeR documentation built on Feb. 5, 2024, 8 a.m.