R/planarityembedding.R

In rlemon: R Access to LEMON Graph Algorithms

##' Checks if an undirected graph is planar.
##'
##' See \url{https://lemon.cs.elte.hu/pub/doc/1.3.1/a00617.html#ga230242aa2ee36f9b1b5a58f2c53016eb}
##' for more information.
##'
##' @title Check if Graph is Planar
##' @param arcSources Vector corresponding to the source nodes of a graph's
##'   edges
##' @param arcTargets Vector corresponding to the destination nodes of a graph's
##'   edges
##' @param numNodes The number of nodes in the graph
##' @return A \code{logical} stating if the graph is planar or not.
##' @export
PlanarChecking <- function(arcSources,
                           arcTargets,
                           numNodes) {

  check_graph_vertices(arcSources, arcTargets, numNodes)

  PlanarCheckingRunner(arcSources, arcTargets, numNodes)
}

##' Checks if an undirected graph is planar and returns a list of outputs
##' related to the planar embedding
##'
##' See \url{https://lemon.cs.elte.hu/pub/doc/1.3.1/a00308.html}
##' for more information.
##'
##' @title Solver for Planar Embedding
##' @param arcSources Vector corresponding to the source nodes of a graph's
##'   edges
##' @param arcTargets Vector corresponding to the destination nodes of a graph's
##'   edges
##' @param numNodes The number of nodes in the graph
##' @return A named list containing 1) "is_planar": a logical indicating if the
##'   graph is planar, 2) "start_nodes_embedding": the start nodes of the arcs
##'   of the embedding, 3) "end_nodes_embedding": the end nodes of the arcs of
##'   the planar embedding, 4) "start_nodes_kuratowski": the start nodes of the
##'   edges of the kuratowski subdivision, 5) "end_nodes_kuratowski": the end
##'   nodes of the edges of the kuratowski subdivision.
##' @export
PlanarEmbedding <- function(arcSources,
                            arcTargets,
                            numNodes) {

  check_graph_vertices(arcSources, arcTargets, numNodes)

  result <- PlanarEmbeddingRunner(arcSources, arcTargets, numNodes)
  result[[1]] <- as.logical(result[[1]])
  names(result) <- c("is_planar", "start_nodes_embedding",
                     "end_nodes_embedding", "start_nodes_kuratowski",
                     "end_nodes_kuratowski")
  return(result)
}

##' Checks if a graph is planar and returns the coloring of the graph
##'
##' See \url{https://lemon.cs.elte.hu/pub/doc/1.3.1/a00306.html}
##' for more information.
##'
##' @title Solver for Planar Coloring
##' @param arcSources Vector corresponding to the source nodes of a graph's
##'   edges
##' @param arcTargets Vector corresponding to the destination nodes of a graph's
##'   edges
##' @param numNodes The number of nodes in the graph
##' @param algorithm, the algorithm to use. "sixColoring" generates a 6-coloring
##'   of the graph, while "fiveColoring" generates a 5-coloring. Default is
##'   "fiveColoring".
##' @return A named list containing 1) "is_planar": a \code{logical} if the
##'   graph is planar, 2) "colors": the color of each vertex of the graph
##' @export
PlanarColoring <- function(arcSources,
                           arcTargets,
                           numNodes,
                           algorithm = "fiveColoring") {

  check_graph_vertices(arcSources, arcTargets, numNodes)
  check_algorithm(algorithm)
  if (!algorithm %in% c("fiveColoring", "sixColoring")) {
    stop("Invalid algorithm.")
  }

  result <- PlanarColoringRunner(arcSources, arcTargets, numNodes,
                                 useFiveAlg = algorithm == "fiveColoring")
  names(result) <- c("is_planar", "colors")
  return(result)
}

##' The planar drawing algorithm calculates positions for the nodes in the
##' plane. These coordinates satisfy that if the edges are represented with
##' straight lines, then they will not intersect each other.
##'
##' See \url{https://lemon.cs.elte.hu/pub/doc/1.3.1/a00307.html}
##' for more information.
##'
##' @title Solver for Planar Drawing
##' @param arcSources Vector corresponding to the source nodes of a graph's
##'   edges
##' @param arcTargets Vector corresponding to the destination nodes of a graph's
##'   edges
##' @param numNodes The number of nodes in the graph
##' @return A named list of 1) "is_planar": a \code{logical} of if the graph is
##'   planar, 2) "x_coords": the x-coordinate of the planar embedding, 3)
##'   "y_coords": the y-coordinate of the planar embedding
##' @export
PlanarDrawing <- function(arcSources,
                          arcTargets,
                          numNodes) {

  check_graph_vertices(arcSources, arcTargets, numNodes)

  result <- PlanarDrawingRunner(arcSources, arcTargets, numNodes)
  names(result) <- c("is_planar", "x_coords", "y_coords")
  return(result)
}