Traverse inward node-by-node until stopping conditions are met

From a graph object of class dgr_graph, move along inward edges from one or more nodes present in a selection to other connected nodes, replacing the current nodes in the selection with those nodes traversed to until reaching nodes that satisfy one or more conditions.

This traversal function makes use of an active selection of nodes. After the traversal, depending on the traversal conditions, there will either be a selection of nodes or no selection at all.

Selections of nodes can be performed using the following node selection (select_*()) functions: select_nodes(), select_last_nodes_created(), select_nodes_by_degree(), select_nodes_by_id(), or select_nodes_in_neighborhood().

Selections of nodes can also be performed using the following traversal (trav_*()) functions: trav_out(), trav_in(), trav_both(), trav_out_node(), trav_in_node(), trav_out_until(), or trav_in_until().

Usage

trav_in_until(
  graph,
  conditions,
  max_steps = 30,
  exclude_unmatched = TRUE,
  add_to_selection = FALSE
)

Arguments

graph: A graph object of class dgr_graph.
conditions: An option to use a stopping condition for the traversal. If the condition is met during the traversal (i.e., the node(s) traversed to match the condition), then those traversals will terminate at those nodes. Otherwise, traversals with continue and terminate when the number of steps provided in max_steps is reached.
max_steps: The maximum number of trav_in() steps (i.e., node-to-node traversals in the inward direction) to allow before stopping.
exclude_unmatched: If TRUE (the default value) then any nodes not satisfying the conditions provided in conditions that are in the ending selection are excluded.
add_to_selection: If TRUE then every node traversed will be part of the final selection of nodes. If FALSE (the default value) then only the nodes finally traversed to will be part of the final node selection.

Value

A graph object of class dgr_graph.

Examples

# Create a path graph and add
# values of 1 to 10 across the
# nodes from beginning to end;
# select the last path node
graph <-
  create_graph() %>%
  add_path(
    n = 10,
    node_data = node_data(
      value = 1:10)) %>%
  select_nodes_by_id(
    nodes = 10)

# Traverse inward, node-by-node
# until stopping at a node where
# the `value` attribute is 1
graph <-
  graph %>%
  trav_in_until(
    conditions =
      value == 1)

# Get the graph's node selection
graph %>% get_selection()
#> [1] 1

# Create two cycles in a graph and
# add values of 1 to 6 to the
# first cycle, and values 7 to
# 12 in the second; select nodes
# `6` and `12`
graph <-
  create_graph() %>%
  add_cycle(
    n = 6,
    node_data = node_data(
      value = 1:6)) %>%
  add_cycle(
    n = 6,
    node_data = node_data(
      value = 7:12)) %>%
  select_nodes_by_id(
    nodes = c(6, 12))

# Traverse inward, node-by-node
# from `6` and `12` until stopping
# at the first nodes where the
# `value` attribute is 1, 2, or 10;
# specify that we should only
# keep the finally traversed to
# nodes that satisfy the conditions
graph <-
  graph %>%
  trav_in_until(
    conditions =
      value %in% c(1, 2, 10),
    exclude_unmatched = TRUE)

# Get the graph's node selection
graph %>% get_selection()
#> [1]  2 10