DiagrammeR (version 0.7)

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

# Before finding out whether a particular edge is present,
# create a simple graph
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)))

edges <-
  create_edges(from = sample(LETTERS, replace = TRUE),
               to = sample(LETTERS, replace = TRUE),
               label = "edge",
               relationship = "letter_to_letter")

graph <-
  create_graph(nodes_df = nodes,
               edges_df = edges,
               graph_attrs = "layout = neato",
               node_attrs = c("fontname = Helvetica",
                              "shape = circle"))

# 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