R/bundle_hammer.R

In schochastics/edgebundle: Algorithms for Bundling Edges in Networks and Visualizing Flow and Metro Maps

#' @title hammer edge bundling
#' @description Implements the hammer edge bundling by Ian Calvert.
#' @details This function only wraps existing python code from the datashader library. Original code can be found at https://gitlab.com/ianjcalvert/edgehammer.
#' Datashader is a huge library with a lot of dependencies, so think twice if you want to install it just for edge bundling.
#' Check https://datashader.org/user_guide/Networks.html for help concerning parameters bw and decay.
#' To install all dependencies, use [install_bundle_py].
#' @param object a graph object (igraph/network/tbl_graph)
#' @param xy coordinates of vertices
#' @param bw bandwidth parameter
#' @param decay decay parameter
#' @return data.frame containing the bundled edges
#' @author David Schoch
#' @details see [online](https://github.com/schochastics/edgebundle) for plotting tips
#' @seealso [edge_bundle_force],[edge_bundle_stub], [edge_bundle_path]
#' @export

edge_bundle_hammer <- function(object, xy, bw = 0.05, decay = 0.7) {
    if (!requireNamespace("reticulate", quietly = TRUE)) {
        stop("The `reticulate` package is required for this functionality")
    }
    if (any(class(object) == "igraph")) {
        if (!requireNamespace("igraph", quietly = TRUE)) {
            stop("The `igraph` package is required for this functionality")
        }
        nodes <- data.frame(name = paste0("node", 0:(igraph::vcount(object) - 1)), x = xy[, 1], y = xy[, 2])
        el <- igraph::get.edgelist(object, names = FALSE)
        el1 <- data.frame(source = el[, 1] - 1, target = el[, 2] - 1)
    } else if (any(class(object) == "tbl_graph")) {
        if (!requireNamespace("tidygraph", quietly = TRUE)) {
            stop("The `tidygraph` package is required for this functionality")
        }
        object <- tidygraph::as.igraph(object)
        nodes <- data.frame(name = paste0("node", 0:(igraph::vcount(object) - 1)), x = xy[, 1], y = xy[, 2])
        el <- igraph::get.edgelist(object, names = FALSE)
        el1 <- data.frame(source = el[, 1] - 1, target = el[, 2] - 1)
    } else if (any(class(object) == "network")) {
        nodes <- data.frame(name = paste0("node", 0:(network::get.network.attribute(object, "n") - 1)), x = xy[, 1], y = xy[, 2])
        el <- network::as.edgelist(object)
        el1 <- data.frame(source = el[, 1] - 1, target = el[, 2] - 1)
    } else {
        stop("only `igraph`, `network` or `tbl_graph` objects supported.")
    }
    data_bundle <- shader_env$datashader_bundling$hammer_bundle(nodes, el1, initial_bandwidth = bw, decay = decay)
    data_bundle$group <- is.na(data_bundle$y) + 0
    data_bundle$group <- cumsum(data_bundle$group) + 1
    data_bundle <- data_bundle[!is.na(data_bundle$y), ]
    data_bundle$index <- unlist(sapply(table(data_bundle$group), function(x) seq(0, 1, length.out = x)))
    data_bundle[, c("x", "y", "index", "group")]
}

#' @title install python dependencies for hammer bundling
#' @description install datashader and scikit-image
#' @param method Installation method (by default, "auto" automatically finds a
#' method that will work in the local environment, but note that the
#' "virtualenv" method is not available on Windows)
#' @param conda Path to conda executable (or "auto" to find conda using the PATH
#' and other conventional install locations)
#' @export
#'
install_bundle_py <- function(method = "auto", conda = "auto") {
    if (!requireNamespace("reticulate", quietly = TRUE)) {
        stop("The `reticulate` package is required for this functionality")
    }
    reticulate::py_install("datashader", method = method, conda = conda, pip = TRUE)
    reticulate::py_install("scikit-image", method = method, conda = conda, pip = TRUE)
}

# Environment for globals
shader_env <- new.env(parent = emptyenv())

.onLoad <- function(libname, pkgname) {
    reticulate::configure_environment(pkgname)
    assign("datashader_bundling", reticulate::import("datashader.bundling", delay_load = TRUE), shader_env)
}