DiagrammeR (version 0.8.4)

get_nodes: Get a vector of node ID values

Description

Obtain a vector of node ID values from a graph object or a node data frame. An optional filter by node attribute can limit the set of node ID values returned.

Usage

get_nodes(x, node_attr = NULL, match = NULL)

Arguments

x

either a graph object of class dgr_graph that is created using create_graph or a node data frame.

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 vector of node ID values.

Examples

# Before getting node ID values, create a
# simple graph
nodes <-
  create_nodes(
    nodes = c("a", "b", "c", "d"),
    type = "letter",
    color = c("red", "green", "grey", "blue"),
    value = c(3.5, 2.6, 9.4, 2.7))

graph <-
  create_graph(nodes_df = nodes)

# Get a vector of all nodes in a graph
get_nodes(graph)
#> [1] "a" "b" "c" "d"

# Get a vector of node ID values from a node
# data frame
get_nodes(nodes)
#> [1] "a" "b" "c" "d"

# Get a vector of node ID values using a numeric
# comparison (i.e., all nodes with 'value' attribute
# greater than 3)
get_nodes(
  graph,
  node_attr = "value",
  match = "> 3")
#> [1] "a" "c"

# Get a vector of node ID values using a match
# pattern (i.e., all nodes with 'color' attribute
# of "green")
get_nodes(
  graph,
  node_attr = "color",
  match = "green")
#> [1] "b"