R/layout_centrality.R

In ggraph: An Implementation of Grammar of Graphics for Graphs and Networks

#' Place nodes in circles according to centrality measure
#'
#' This layout places nodes in circles with the radii relative to a given
#' centrality measure. Under the hood it use stress majorisation to place nodes
#' optimally given the radius constraint.
#'
#' @param graph A tbl_graph object
#' @param centrality An expression evaluating to a centrality measure for the
#' nodes. See the different `centrality_*()` algorithms in tidygraph for a
#' selection.
#' @param scale Should the centrality measure be scaled between 0 and 100
#' @param tseq Transitioning steps
#' @param group An expression evaluating to a grouping of the nodes. If given
#' the layout will keep grouped nodes within an angle range of the origin
#' @param shrink shrink the reserved angle range for a group to increase the
#' gaps between groups
#' @inheritParams layout_tbl_graph_stress
#'
#' @return A data.frame with the columns `x`, `y`, `circular`, `centrality` as
#' well as any information stored as node variables in the tbl_graph object.
#'
#' @references
#' Brandes, U., & Pich, C. (2011). *More flexible radial layout.* Journal of
#' Graph Algorithms and Applications, 15(1), 157-173.
#'
#' @family layout_tbl_graph_*
#'
#' @author The underlying algorithm is implemented in the graphlayouts package
#' by David Schoch
#'
#' @importFrom graphlayouts layout_with_centrality layout_with_centrality_group
#' @importFrom rlang eval_tidy enquo
layout_tbl_graph_centrality <- function(graph, centrality, scale = TRUE,
                                        niter = 500, tolerance = 1e-4,
                                        tseq = seq(0,1,0.2), group = NULL,
                                        shrink = 10, circular = FALSE) {
  centrality <- eval_tidy(enquo(centrality), .N())
  group <- eval_tidy(enquo(group), .N())
  if (is.null(group)) {
    xy <- layout_with_centrality(graph, cent = centrality, scale = scale,
                                 iter = niter, tol = tolerance, tseq = tseq)
  } else {
    xy <- layout_with_centrality_group(graph, cent = centrality, group = group,
                                       shrink = shrink, scale = scale,
                                       iter = niter, tol = tolerance,
                                       tseq = tseq)
  }

  nodes <- data_frame0(x = xy[,1],y = xy[,2], centrality = centrality,
                       group = group, circular = FALSE)
  combine_layout_nodes(nodes, as_tibble(graph, active = 'nodes'))
}