DiagrammeR (version 0.9.0)

edge_present: Determine whether a specified edge is present in an existing graph object

Description

From a graph object of class dgr_graph, determine whether a directed edge (defined by a pair of node IDs extant in the graph) is present.

Usage

edge_present(graph, from, to)

Arguments

graph

a graph object of class dgr_graph.

from

a node ID from which the edge to be queried is outgoing.

to

a node ID to which the edge to be queried is incoming.

Value

a logical value.

Examples

# NOT RUN {
# Set a seed
set.seed(24)

# Create a node data frame (ndf)
ndf <-
  create_node_df(
    n = 26,
    label = TRUE,
    type = c(rep("a", 7),
             rep("b", 9),
             rep("c", 8),
             rep("d", 2)))

# Create an edge data frame (edf)
edf <-
  create_edge_df(
    from = sample(1:26, replace = TRUE),
    to = sample(1:26, replace = TRUE),
    rel = c(rep("rel_a", 7),
            rep("rel_b", 9),
            rep("rel_c", 8),
            rep("rel_d", 2)))

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

# Is there any edge between nodes with IDs
# `1` and `2`?
edge_present(graph, from = 1, to = 2)
#> FALSE

# Verify that there is an edge between nodes
# `18` and `26`
edge_present(graph, from = 18, to = 26)
#> TRUE
# }