DiagrammeR (version 0.8.4)

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 that is created using create_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

# Create a node data frame (ndf)
nodes <-
  create_nodes(
    nodes = LETTERS,
    label = TRUE,
    type = c(rep("a_to_g", 7),
             rep("h_to_p", 9),
             rep("q_to_x", 8),
             rep("y_and_z", 2)))

# Create an edge data frame (edf)
edges <-
  create_edges(
    from = sample(LETTERS, replace = TRUE),
    to = sample(LETTERS, replace = TRUE),
    rel = "letter_to_letter")

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

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

# Verify that there is an edge between nodes
# `K` and `V`
edge_present(graph, from = "K", to = "V")
#> TRUE