DiagrammeR (version 1.0.9)

select_nodes_by_degree: Select nodes in the graph based on their degree values

Description

Using a graph object of class dgr_graph, create a selection of nodes that have certain degree values.

Usage

select_nodes_by_degree(graph, expressions, set_op = "union")

Value

A graph object of class dgr_graph.

Arguments

graph

A graph object of class dgr_graph.

expressions

One or more expressions for filtering nodes by degree values. Use a combination of degree type (deg for total degree, indeg for in-degree, and outdeg for out-degree) with a comparison operator and values for comparison (e.g., use "deg >= 2" to select nodes with a degree greater than or equal to 2).

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.

Examples

# Create a random graph using
# the `add_gnm_graph()` function
graph <-
  create_graph() %>%
  add_gnm_graph(
    n = 35, m = 125,
    set_seed = 23)

# Report which nodes have a
# total degree (in-degree +
# out-degree) of exactly 9
graph %>%
  select_nodes_by_degree(
    expressions = "deg == 9") %>%
  get_selection()

# Report which nodes have a
# total degree greater than or
# equal to 9
graph %>%
  select_nodes_by_degree(
    expressions = "deg >= 9") %>%
  get_selection()

# Combine two calls of
# `select_nodes_by_degree()` to
# get those nodes with total
# degree less than 3 and total
# degree greater than 10 (by
# default, those `select...()`
# functions will `union` the
# sets of nodes selected)
graph %>%
  select_nodes_by_degree(
    expressions = "deg < 3") %>%
  select_nodes_by_degree(
    expressions = "deg > 10") %>%
  get_selection()

# Combine two calls of
# `select_nodes_by_degree()` to
# get those nodes with total
# degree greater than or equal
# to 3 and less than or equal
# to 10 (the key here is to
# `intersect` the sets of nodes
# selected in the second call)
graph %>%
  select_nodes_by_degree(
    expressions = "deg >= 3") %>%
  select_nodes_by_degree(
    expressions = "deg <= 10",
    set_op = "intersect") %>%
  get_selection()

# Select all nodes with an
# in-degree greater than 5, then,
# apply a node attribute to those
# selected nodes (coloring the
# selected nodes red)
graph_2 <-
  graph %>%
  select_nodes_by_degree(
    expressions = "indeg > 5") %>%
  set_node_attrs_ws(
    node_attr = color,
    value = "red")

# Get the selection of nodes
graph_2 %>% get_selection()