DiagrammeR (version 0.8.4)

select_edges_by_node_id: Select edges in a graph using node ID values

Description

Select edges in a graph object of class dgr_graph using node ID values. All edges associated with the provided nodes will be included in the selection. If nodes have IDs that are monotonically increasing integer values, then numeric ranges can be provided for the selection.

Usage

select_edges_by_node_id(graph, nodes, set_op = "union")

Arguments

graph

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

nodes

a vector of node IDs for the selection of nodes present in the graph.

set_op

the set operation to perform upon consecutive selections of graph nodes. This can either be as a union (the default), as an intersection of selections with intersect, or, as a difference on the previous selection, if it exists.

Value

a graph object of class dgr_graph.

Examples

library(magrittr)

# Create a graph with a tree structure that's
# 3 levels deep (begins with node `1`, branching
# by 3 nodes at each level); the resulting graph
# contains 13 nodes, numbered `1` through `13`
graph <-
  create_graph(graph_attrs = 'layout = twopi') %>%
  add_node("A") %>%
  select_nodes %>%
  add_n_nodes_ws(3, "from", "B") %>%
  clear_selection %>%
  select_nodes("type", "B") %>%
  add_n_nodes_ws(3, "from", "C") %>%
  clear_selection

# Create a graph selection by selecting edges
# associated with nodes `1` and `2`
graph %<>%
  select_edges_by_node_id(
    nodes = 1:2)

# Get the selection of edges
graph %>% get_selection
#> $edges
#> $edges$from
#> [1] "1" "1" "1" "2" "2" "2"
#>
#> $edges$to
#> [1] "2" "3" "4" "5" "6" "7"

# Perform another selection of nodes, this time
# with a neighborhood spanning 2 nodes from node `1`
graph %<>%
  clear_selection %>%
  select_edges_by_node_id(
    nodes = c(1, 2, 4))

# Get the selection of edges
graph %>% get_selection
#> $edges
#> $edges$from
#> [1] "1" "1" "1" "2" "2" "2" "4" "4" "4"
#>
#> $edges$to
#> [1] "2"  "3"  "4"  "5"  "6"  "7"  "11" "12" "13"

# Get a fraction of the edges selected over all
# the edges in the graph
graph %>%
{
  l <- get_selection(.) %>%
    unlist(.) %>%
    length(.) %>%
    divide_by_int(2)
  e <- edge_count(.)
  l/e
}
#> [1] 0.75