DiagrammeR (version 0.8.4)

get_edges: Get node IDs associated with edges

Description

Obtain a vector, data frame, or list of node IDs from a graph object or an edge data frame. An optional filter by edge attribute can limit the set of edges returned.

Usage

get_edges(x, edge_attr = NULL, match = NULL, return_type = "vector")

Arguments

x

either a graph object of class dgr_graph that is created using create_graph or an edge data frame.

edge_attr

an optional character vector of edge attribute values for filtering the edges returned.

match

an option to provide a logical expression with a comparison operator (>, <, ==, or !=) followed by a number for numerical filtering, or, a character string for filtering the edges returned through string matching.

return_type

using vector (the default), a vector of character objects representing the edges is provided. With list a list object will be provided that contains vectors of outgoing and incoming node IDs associated with edges. With df, a data frame containing outgoing and incoming node IDs associated with edges.

Value

a list, data frame, or a vector object, depending on the value given to return_type.

Examples

# Create a node data frame (ndf)
nodes <-
  create_nodes(
    nodes = c("a", "b", "c", "d"),
    type = "letter",
    color = c("red", "green", "grey", "blue"),
    value = c(3.5, 2.6, 9.4, 2.7))

# Create an edge data frame (edf)
edges <-
  create_edges(
    from = c("a", "b", "c"),
    to = c("d", "c", "a"),
    rel = "leading_to",
    color = c("pink", "blue", "red"),
    value = c(3.9, 2.5, 7.3))

# Create a graph
graph <-
  create_graph(
    nodes_df = nodes,
    edges_df = edges)

# Get all edges within a graph, returned as a list
get_edges(graph)
#> [[1]]
#> [1] "a" "b" "c"
#>
#> [[2]]
#> [1] "d" "c" "a"

# Get all edges within a graph, returned as a
# data frame
get_edges(graph, return_type = "df")
#>   from to
#> 1    a  d
#> 2    b  c
#> 3    c  a

# Get all edges within a graph, returned as a vector
get_edges(graph, return_type = "vector")
#> [1] "a -> d" "b -> c" "c -> a"

# Get a vector of edges using a numeric
# comparison (i.e., all edges with a `value`
# attribute greater than 3)
get_edges(
  graph,
  edge_attr = "value",
  match = "> 3",
  return_type = "vector")
#> [1] "a -> d" "c -> a"

# Get a vector of edges using a match
get_edges(
  graph,
  edge_attr = "color",
  match = "pink",
  return_type = "vector")
#> [1] "a -> d"