DiagrammeR (version 0.8.4)

select_nodes: Select nodes in a graph

Description

Select nodes from a graph object of class dgr_graph.

Usage

select_nodes(graph, node_attr = NULL, search = NULL, set_op = "union", nodes = 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.

search

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

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.

nodes

an optional vector of node IDs for filtering list of nodes present in the graph.

Value

a graph object of class dgr_graph.

Examples

library(magrittr)

# Create a node data frame (ndf)
nodes <-
  create_nodes(
    nodes = c("a", "b", "c", "d"),
    type = c("A", "A", "Z", "Z"),
    label = TRUE,
    value = c(3.5, 2.6, 9.4, 2.7))

# Create an edge data frame (edf)
edges <-
  create_edges(
    from = c("a", "b", "c"),
    to = c("d", "c", "a"),
    rel = c("A", "Z", "A"))

# Create a graph with the ndf and edf
graph <-
  create_graph(nodes_df = nodes,
               edges_df = edges)

# Explicitly select nodes `a` and `c`
graph <-
  graph %>%
  select_nodes(
    nodes = c("a", "c"))

# Verify that the node selection has been made
# using the `get_selection()` function
get_selection(graph)
#> $nodes
#> [1] "a" "c"

# Select nodes based on the node `type`
# being `Z`
graph <-
  graph %>%
  clear_selection %>%
  select_nodes(
    node_attr = "type",
    search = "Z")

# Verify that an node selection has been made, and
# recall that the `c` and `d` nodes are of the
# `Z` type
get_selection(graph)
#> $nodes
#> [1] "c" "d"

# Select edges based on the node value attribute
# being greater than 3.0 (first clearing the current
# selection of nodes)
graph <-
  graph %>%
  clear_selection %>%
  select_nodes(
    node_attr = "value",
    search = ">3.0")

# Verify that the correct node selection has been
# made; in this case, nodes `a` and `c` have values
# for `value` greater than 3.0
get_selection(graph)
#> $nodes
#> [1] "a" "c"