DiagrammeR (version 0.9.0)

delete_edge: Delete an edge from an existing graph object

Description

From a graph object of class dgr_graph, delete an existing edge by specifying either: (1) a pair of node IDs corresponding to the edge (keeping into consideration the direction of the edge in a directed graph), or (2) an edge ID.

Usage

delete_edge(graph, from = NULL, to = NULL, id = NULL)

Arguments

graph

a graph object of class dgr_graph.

from

a node ID from which the edge to be removed is outgoing. If an edge ID is provided to id, then this argument is ignored.

to

a node ID to which the edge to be removed is incoming. If an edge ID is provided to id, then this argument is ignored.

id

an edge ID of the edge to be removed.

Value

a graph object of class dgr_graph.

Examples

# NOT RUN {
# Create an empty graph
graph <- create_graph()

# Add two nodes
graph <- add_node(graph)
graph <- add_node(graph)

# Add an edge
graph <-
  add_edge(
    graph = graph,
    from = 1,
    to = 2)

# Delete the edge
graph <-
  delete_edge(
    graph = graph,
    from = 1,
    to = 2)

# Get the count of edges in the graph
edge_count(graph)
#> [1] 0

# Create an undirected graph with
# 2 nodes and an edge
graph_undirected <-
  create_graph(directed = FALSE) %>%
  add_n_nodes(2) %>%
  add_edge(1, 2)

# Delete the edge; order of node ID
# values provided in `from` and `to`
# don't matter for the undirected case
graph_undirected %>%
  delete_edge(2, 1) %>%
  edge_count()
#> [1] 0

graph_undirected %>%
  delete_edge(1, 2) %>%
  edge_count()
#> [1] 0

# The undirected graph has a single
# edge with ID `1`; it can be
# deleted by specifying `id`
graph_undirected %>%
  delete_edge(id = 1) %>%
  edge_count()
#> [1] 0
# }