DiagrammeR (version 0.8.4)

trav_out: Traverse outward from a selected node, skipping over edges, and creating a new node selection

Description

From a graph object of class dgr_graph move outward from one or more nodes present in a selection to other nodes, replacing the current nodes in the selection with those nodes traversed to.

Usage

trav_out(graph, node_attr = NULL, match = NULL)

Arguments

graph

a graph object of class dgr_graph that is created using create_graph.

node_attr

an optional character vector of node attribute values for filtering the node ID values returned.

match

an option to provide a logical expression with a comparison operator (>, <, ==, or !=) followed by a number for numerical filtering, or, a character string for filtering the edges returned through string matching.

Value

a graph object of class dgr_graph.

Examples

## Not run: 
# library(magrittr)
# 
# # Create a graph
# graph <-
# create_graph() %>%
#   add_n_nodes(4) %>%
#   add_edge(1, 2) %>%
#   add_edge(2, 3) %>%
#   add_edge(3, 4)
# 
# # Starting at node `1`, traverse to node `4`,
# # storing the traversed location as a selection in
# # the graph object
# graph <-
#   graph %>%
#   select_nodes_by_id(1) %>%
#   trav_out %>% trav_out %>% trav_out
# 
# # Verify that the selection has been made by using
# # the `get_selection()` function
# get_selection(graph)
# #> [1] "4"
# 
# # Modify the graph by adding `type` values for
# # each of the nodes (recall that node `4` is now
# # selected since the traversal ended at that node)
# graph <-
#   graph %>%
#   set_node_attrs_ws(
#     node_attr = "type", value = "z") %>%
#   clear_selection %>%
#   select_nodes_by_id(1:3) %>%
#   set_node_attrs_ws(
#     node_attr = "type", value = "a") %>%
#   clear_selection
# 
# # When traversing outward from node `3` to `4`,
# # you can set a condition that determines whether
# # such traversal is permitted; in this case the
# # condition is to traverse only to nodes where
# # the type value is set to `a` (but node `4` has
# # its `type` set to `z`, so, no traversal)
# graph %>%
#   select_nodes_by_id(3) %>%
#   trav_out("type", "a") %>%
#   get_selection
# #> [1] "3"
# 
# # Setting the condition to traverse only to nodes
# # where the type is `z` will result in a traversal
# graph %>%
#   select_nodes_by_id(3) %>%
#   trav_out("type", "z") %>%
#   get_selection
# #> [1] "4"
# 
# # We can also set traversal conditions to satisfy
# # numeric comparisons... the graph will be first
# # modified
# graph <-
#   graph %>%
#   set_node_attrs(1, "value", 3.4) %>%
#   set_node_attrs(2, "value", 6.7) %>%
#   set_node_attrs(3, "value", 9.1) %>%
#   set_node_attrs(4, "value", 2.5)
# 
# # Traverse from nodes `1` to `4`, setting the
# # condition that each node traversed to must have
# # a `value` greater than 3.0 (although 3 separate
# # traversals are intended, the last traversal does
# # not reach node `4` since its value is not
# # greater than 3.0)
# graph %>%
#   select_nodes_by_id(1) %>%
#   trav_out("value", ">3.0") %>%
#   trav_out("value", ">3.0") %>%
#   trav_out("value", ">3.0") %>%
#   get_selection
# #> [1] "3"
# ## End(Not run)