R/open_graph.R

In DiagrammeR: Graph/Network Visualization

#' Read a graph or graph series from disk
#'
#' @description
#'
#' Load a graph or a graph series object from disk.
#'
#' @param file The filename for the graph or graph series. Optionally, this may
#'   contain a path to the file.
#' @examples
#' # Create an undirected GNP
#' # graph with 100 nodes using
#' # a probability value of 0.05
#' gnp_graph <-
#'   create_graph(
#'     directed = FALSE) %>%
#'   add_gnp_graph(
#'     n = 100,
#'     p = 0.05
#'   )
#'
#' # Save the graph to disk; use
#' # the file name `gnp_graph.dgr`
#' # save_graph(
#' #   x = gnp_graph,
#' #   file = "gnp_graph"
#' # )
#'
#' # To read the graph file from
#' # disk, use `open_graph()`
#' # gnp_graph_2 <-
#' #   open_graph(
#' #     file = "gnp_graph.dgr"
#' #   )
#'
#' @export
open_graph <- function(file) {

  # Get the name of the function
  fcn_name <- get_calling_fcn()

  if (!inherits(file, "character")) {

    emit_error(
      fcn_name = fcn_name,
      reasons = "Provide a character string for the file")
  }

  # Read the graph or graph series
  x <- readRDS(file = file)

  if (inherits(x, "dgr_graph") |
      inherits(x, "dgr_graph_1D")) {

    return(x)

  } else {

    emit_error(
      fcn_name = fcn_name,
      reasons = "The object opened is not a graph or graph series")
  }
}