From a graph object of class `dgr_graph`

, determine whether an edge (defined
by a pair of node IDs or node label values) is present.

## Arguments

- graph
A graph object of class

`dgr_graph`

.- edge
An edge ID value to test for presence in the graph. If a single, numeric value is provided then values for

`from`

or`to`

needn't be supplied.- from
A node ID from which the edge is outgoing, or, the label associated with the node. For an undirected graph, the value in

`from`

can be interchangeable with that in`to`

.- to
A node ID to which the edge is incoming, or, the label associated with the node. For an undirected graph, the value in

`to`

can be interchangeable with that in`from`

.

## Examples

```
# Create a simple graph with
# a path of four nodes
graph <-
create_graph() %>%
add_path(
n = 4,
type = "path",
label = c("one", "two",
"three", "four"))
# Find out if edge ID `3`
# is present in the graph
graph %>%
is_edge_present(edge = 3)
#> [1] TRUE
# Determine if there are any edges
# with the definition `1` -> `2`
graph %>%
is_edge_present(
from = 1,
to = 2)
#> [1] TRUE
# Determine if there are any edges
# with the definition `4` -> `5`
graph %>%
is_edge_present(
from = 4,
to = 5)
#> [1] FALSE
# Determine whether an edge,
# defined by its labels as
# `two` -> `three`, exists in
# the graph
graph %>%
is_edge_present(
from = "two",
to = "three")
#> [1] TRUE
# Set the graph as undirected
# and determine whether an
# edge between nodes with labels
# `three` and `two` exists
graph %>%
set_graph_undirected() %>%
is_edge_present(
from = "three",
to = "two")
#> [1] TRUE
```