R/get_edge_count_w_multiedge.R

In DiagrammeR: Graph/Network Visualization

#' Get count of edge definitions where multiple edges occur
#'
#' @description
#'
#' Get a count of the number of edge definitions (e.g, `1` -> `2`) where there
#' are multiple edges (i.e., more than 1 edge of that definition, having
#' distinct edge ID values). So, for example, if there are 2 edge definitions in
#' the graph that involve 6 separate edge IDs (3 such edge IDs for each of the
#' pairs of nodes), the count will be `2`.
#'
#' @inheritParams render_graph
#'
#' @return A vector with a single, numerical value.
#'
#' @examples
#' # Create a node data frame (ndf)
#' ndf <-
#'   create_node_df(
#'     n = 5,
#'     label = TRUE)
#'
#' # Create an edge data frame (edf)
#' edf <-
#'   create_edge_df(
#'     from = c(1, 4, 4, 3, 5, 1, 3, 4),
#'       to = c(4, 1, 1, 2, 2, 2, 2, 1))
#'
#' # Create a graph with the ndf and edf
#' graph <-
#'   create_graph(
#'     nodes_df = ndf,
#'     edges_df = edf)
#'
#' # Get the total number of edge
#' # definitions (e.g., `4` -> `1`) where
#' # there are multiple edges (i.e.,
#' # distinct edges with separate edge
#' # ID values)
#' graph %>% get_edge_count_w_multiedge()
#'
#' @export
get_edge_count_w_multiedge <- function(graph) {

  # Validation: Graph object is valid
  check_graph_valid(graph)

  # Validation: Graph contains edges
  check_graph_contains_edges(graph)

  # Check for the number of multiple edges
  # regardless of which definitions these
  # edges have
  multiedge_distinct_edge_def_count <-
    graph$edges_df %>%
    dplyr::select(from, to) %>%
    dplyr::mutate(edge_from_to = paste0(from, "_", to), .keep = "none") %>%
    dplyr::group_by(edge_from_to) %>%
    dplyr::summarize(n = dplyr::n(), .groups = "drop") %>%
    dplyr::filter(n > 1) %>%
    nrow()

  multiedge_distinct_edge_def_count
}