delete_edge {DiagrammeR}R Documentation

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. There is the option to use a node label value here (and this must correspondingly also be done for the to argument) for defining node connections. Note that this is only possible if all nodes have distinct label values set and none exist as an empty string.

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. There is the option to use a node label value here (and this must correspondingly also be for the from argument) for defining node connections. Note that this is only possible if all nodes have distinct label values set and none exist as an empty string.

id

an edge ID of the edge to be removed.

Value

a graph object of class dgr_graph.

Examples

# Create a graph with 2 nodes
graph <-
  create_graph() %>%
  add_n_nodes(n = 2)

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

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

# Get the count of edges in the graph
graph %>%
  count_edges()

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

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

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

# Create a directed graph with 2
# labeled nodes and an edge
graph_labeled_nodes <-
  create_graph() %>%
  add_n_nodes(
    n = 2,
    label = c("one", "two")) %>%
  add_edge(
    from = "one",
    to = "two")

# Delete the edge using the node
# labels in `from` and `to`; this
# is analogous to creating the
# edge using node labels
graph_labeled_nodes %>%
  delete_edge(
    from = "one",
    to = "two") %>%
  count_edges()
[Package DiagrammeR version 1.0.1 Index]