DiagrammeR (version 0.8.4)

trav_in_edge: Traverse from one or more selected nodes onto adjacent, inward edges

Description

From a graph object of class dgr_graph move to incoming edges from a selection of one or more selected nodes, thereby creating a selection of edges. An optional filter by edge attribute can limit the set of edges traversed to.

Usage

trav_in_edge(graph, edge_attr = NULL, match = NULL)

Arguments

graph

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

edge_attr

an optional character vector of edge 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

library(magrittr)

# Create a simple graph
graph <-
 create_graph() %>%
 add_n_nodes(4) %>%
 add_edge(1, 2) %>%
 add_edge(2, 3) %>%
 add_edge(3, 4)

# Traverse from nodes `4` to to `1` by, in an
# alternating manner, moving from nodes onto edges,
# from edges onto nodes
graph <-
  graph %>%
  select_nodes_by_id(4) %>%
  trav_in_edge %>%
  trav_out_node %>%
  trav_in_edge %>%
  trav_out_node %>%
  trav_in_edge %>%
  trav_out_node

# Verify that the selection has been made by using
# the `get_selection()` function
get_selection(graph)
#> [1] "1"