add_reverse_edges_ws {DiagrammeR} | R Documentation

## Add new edges in the opposite directions of a selection of edges

### Description

Add edges in the opposite direction of one or more edges available as an edge selection in a graph object of class `dgr_graph`. New graph edges have the opposite edge definitions as those in the selection. For example, a graph with the edge `1->2` in its active selection will gain a new `2->1` edge. There is also the option to assign a common `rel` grouping to the newly created edges. Upon addition of the edges, the edge selection will be retained for further selection or traversal operations.

Selections of edges can be performed using the following `select_...` functions: `select_edges()`, `select_last_edge()`, or `select_edges_by_node_id()`. Selections of edges can also be performed using the following traversal functions: `trav_out_edge()`, `trav_in_edge()`, or `trav_both_edge()`.

### Usage

    add_reverse_edges_ws(graph, rel = NULL)

### Arguments

`graph` | a graph object of class `dgr_graph`.
`rel` | an optional string to apply a `rel` attribute to all newly created edges.

### Value

a graph object of class `dgr_graph`.

### Examples

    # Create an empty graph, add 2 nodes to it,
    # and create the edge `1->2`
    graph <-
      create_graph() %>%
      add_n_nodes(
        n = 2,
        type = "type_a",
        label = c("a_1", "a_2")) %>%
      add_edge(
        from = 1,
        to = 2,
        rel = "a")

    # Get the graph's edges
    graph %>%
      get_edge_ids()
    #> [1] 1

    # Select the edge and create 2 additional edges
    # with the opposite definition of `1->2`, which
    # is `2->1`; also, apply, different `rel` values
    # (`b` and `c`)
    graph <-
      graph %>%
      select_edges() %>%
      add_reverse_edges_ws(rel = "b") %>%
      add_reverse_edges_ws(rel = "c") %>%
      clear_selection()

    # Get the graph's edge data frame
    get_edge_df(graph)
    #>   id from to rel
    #> 1  1    1  2   a
    #> 2  2    2  1   b
    #> 3  3    2  1   c

[Package DiagrammeR version 0.9.2 Index]