DiagrammeR (version 0.9.2)

add_edge: Add an edge between nodes in a graph object

Description

With a graph object of class dgr_graph, add an edge to nodes within the graph.

Usage

add_edge(graph, from, to, rel = NULL, ...)

Arguments

graph

a graph object of class dgr_graph.

from

the outgoing node from which the edge is connected. 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

the incoming nodes to which each edge is connected. There is the option to use a node label value here (and this must correspondingly also be done 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.

rel

an optional string specifying the relationship between the connected nodes.

...

optional edge attributes supplied as vectors.

Value

a graph object of class dgr_graph.

Examples

# NOT RUN {
# Create a graph with 4 nodes
graph <-
  create_graph() %>%
  add_node(label = "one") %>%
  add_node(label = "two") %>%
  add_node(label = "three") %>%
  add_node(label = "four")

# Add an edge between those nodes and attach a
# relationship to the edge
graph <-
 add_edge(
   graph,
   from = 1,
   to = 2,
   rel = "A")

# Use the `edge_info()` function to verify that
# the edge has been created
edge_info(graph)
#>   id from to rel
#> 1  1    1  2   A

# Add another node and edge to the graph
graph <-
  graph %>%
  add_edge(
    from = 3,
    to = 2,
    rel = "A")

# Verify that the edge has been created by
# getting a count of graph edges
edge_count(graph)
#> [1] 2

# Add edges by specifying node `label`
# values; note that all nodes must have
# unique `label` values to use this option
graph <-
  graph %>%
  add_edge(
    from = "three",
    to = "four",
    rel = "L") %>%
  add_edge(
    from = "four",
    to = "one",
    rel = "L")

# Use the `get_edges()` function to verify
# that the edges were added
get_edges(graph)
#> [1] "1->2" "3->2" "3->4" "4->1"
# }