R/get_max_eccentricity.R

In rich-iannone/DiagrammeR: Graph/Network Visualization

#' Get the maximum graph eccentricity
#'
#' @description
#'
#' Get the diameter of a graph, which is the largest eccentricity in the graph.
#' The graph eccentricity of a node is its shortest path from the farthest other
#' node in the graph.
#'
#' @inheritParams render_graph
#'
#' @return A single numeric value representing the maximum eccentricity of the
#'   graph.
#'
#' @examples
#' # Create a cycle graph
#' graph <-
#'   create_graph() %>%
#'   add_cycle(n = 5)
#'
#' # Determine the graph's maximum
#' # eccentricity
#' graph %>%
#'   get_max_eccentricity()
#'
#' # Create a full graph and then
#' # get the maximum eccentricity
#' # value for that
#' create_graph() %>%
#'   add_full_graph(n = 10) %>%
#'   get_max_eccentricity()
#'
#' @export
get_max_eccentricity <- function(graph) {

  # Validation: Graph object is valid
  check_graph_valid(graph)

  # If the graph is empty, then return NA
  if (nrow(graph$nodes_df) == 0) {
    return(NA_real_)
  }

  # Convert the graph to an igraph object
  ig_graph <- to_igraph(graph)

  # Get the maximum eccentricity of the graph
  igraph::diameter(ig_graph)
}