Get the graph reciprocity

Description

Get the reciprocity of a directed graph. The reciprocity of a graph is the fraction of reciprocal edges (e.g., '1' -> '2' and '2' -> '1') over all edges available in the graph. Note that for an undirected graph, all edges are reciprocal. This function does not consider loop edges (e.g., '1' -> '1').

Usage

get_reciprocity(graph)

Arguments

Value

a single, numerical value that is the ratio value of reciprocal edges over all graph edges.

Examples

# Define a graph where 2 edge definitions
# have pairs of reciprocal edges
graph <-
  create_graph() %>%
  add_cycle(n = 3) %>%
  add_node(
    from = 1,
      to = 1) %>%
  add_node(
    from = 1,
      to = 1)

# Get the graph reciprocity, which will
# be calculated as the ratio 4/7 (where
# 4 is the number reciprocating edges
# and 7 is the total number of edges
# in the graph)
graph %>%
  get_reciprocity()

# For an undirected graph, all edges
# are reciprocal, so the ratio will
# always be 1
graph %>%
  set_graph_undirected() %>%
  get_reciprocity()

# For a graph with no edges, the graph
# reciprocity cannot be determined (and
# the same NA result is obtained from an
# empty graph)
create_graph() %>%
  add_n_nodes(n = 5) %>%
  get_reciprocity()