Add an edge between nodes in a graph object

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

add_edge(graph, from, to, rel = NULL, edge_aes = NULL, edge_data = 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.

edge_aes

An optional list of named vectors comprising edge aesthetic attributes. The helper function edge_aes() is strongly recommended for use here as it contains arguments for each of the accepted edge aesthetic attributes (e.g., shape, style, penwidth, color).

edge_data

An optional list of named vectors comprising edge data attributes. The helper function edge_data() is strongly recommended for use here as it helps bind data specifically to the created edges.

Value

A graph object of class dgr_graph.

See also

Other edge creation and removal: add_edge_clone(), add_edge_df(), add_edges_from_table(), add_edges_w_string(), add_forward_edges_ws(), add_reverse_edges_ws(), copy_edge_attrs(), create_edge_df(), delete_edge(), delete_edges_ws(), delete_loop_edges_ws(), drop_edge_attrs(), edge_data(), join_edge_attrs(), mutate_edge_attrs(), mutate_edge_attrs_ws(), recode_edge_attrs(), rename_edge_attrs(), rescale_edge_attrs(), rev_edge_dir(), rev_edge_dir_ws(), set_edge_attr_to_display(), set_edge_attrs(), set_edge_attrs_ws()

Examples

# 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 `get_edge_info()`
# function to verify that
# the edge has been created
graph %>%
  get_edge_info()
#>   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
# counting graph edges
graph %>% count_edges()
#> [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 `get_edges()` to verify
# that the edges were added
graph %>% get_edges()
#> [1] "1->2" "3->2" "3->4" "4->1"

# Add edge aesthetic and data
# attributes during edge creation
graph_2 <-
  create_graph() %>%
  add_n_nodes(n = 2) %>%
  add_edge(
    from = 1,
    to = 2,
    rel = "M",
    edge_aes = edge_aes(
      penwidth = 1.5,
      color = "blue"),
    edge_data = edge_data(
      value = 4.3))

# Use the `get_edges()` function
# to verify that the attribute
# values were bound to the
# newly created edge
graph_2 %>% get_edge_df()
#>   id from to rel penwidth color value
#> 1  1    1  2   M      1.5  blue   4.3