add R implementation of fast non-dominated sorting algorithm

NAMESPACE

@@ -8,6 +8,7 @@ S3method(getSupportedRepresentations,ecr_operator)
 S3method(is.supported,ecr_operator)
 S3method(print,ecr_control)
 S3method(print,ecr_result)
+export(doNondominatedSorting)
 export(doTheEvolution)
 export(dominates)
 export(getBestIndividual)

R/doNondominatedSorting.R

@@ -0,0 +1,67 @@
+#' Implementation of the fast non-dominated sorting algorithm proposed by Deb.
+#'
+#' @param x [\code{matrix}]\cr
+#'   Numeric matrix of points. Each row contains on points.
+#' @return [\code{list}]
+#'   List with the following components
+#'   \describe{
+#'     \item{ranks}{Integer vector of ranks of length \code{nrow(x)}. The higher
+#'     the rank, the higher the domination front the corresponding points is
+#'     located on.}
+#'     \item{dom.counter}{Integer vector of length \code{nrow(x)}. The i-th element
+#'     is the domination counter / domination number of the i-th point.}
+#'   }
+#' @export
+#FIXME: [later] implement this in C(++)
+doNondominatedSorting = function(x) {
+  # initialize domination front wrapper
+  fronts = list()
+  fronts[[1L]] = list()
+
+  n = nrow(x)
+  dom.counter = integer(n)
+  ranks = integer(n)
+  dom.els = vector(mode = "list", length = n)
+
+  # compute domination numbers and pareto front
+  for (i in seq.int(n)) {
+    for (j in seq.int(n)) {
+      if (dominates(x[i, ], x[j, ])) {
+        dom.els[[i]] = c(dom.els[[i]], j)
+      } else if (isDominated(x[i, ], x[j, ])) {
+        dom.counter[i] = dom.counter[i] + 1L
+      }
+    }
+    # in this case point x_i belongs to the pareto front, i.e., domination layer 1
+    if (dom.counter[i] == 0L) {
+      ranks[i] = 1L
+      fronts[[1L]] = c(fronts[[1L]], i)
+    }
+  }
+
+  # make a copy of the dominations number since we are going to modify these
+  # in the next lines, but also want to return them
+  dom.counter2 = dom.counter
+
+  # now compute the remaining domination fronts
+  k = 1L
+  while (length(fronts[[k]]) > 0L) {
+    front2 = list()
+    for (i in fronts[[k]]) {
+      for (j in dom.els[[i]]) {
+        dom.counter[j] = dom.counter[j] - 1L
+        if (dom.counter[j] == 0L) {
+          ranks[j] = k + 1L
+          front2 = c(front2, j)
+        }
+      }
+    }
+    k = k + 1L
+    fronts[[k]] = front2
+  }
+
+  return(list(
+    ranks = ranks,
+    dom.counter = dom.counter
+  ))
+}

man/doNondominatedSorting.Rd

@@ -0,0 +1,27 @@
+% Generated by roxygen2 (4.1.1): do not edit by hand
+% Please edit documentation in R/doNondominatedSorting.R
+\name{doNondominatedSorting}
+\alias{doNondominatedSorting}
+\title{Implementation of the fast non-dominated sorting algorithm proposed by Deb.}
+\usage{
+doNondominatedSorting(x)
+}
+\arguments{
+\item{x}{[\code{matrix}]\cr
+Numeric matrix of points. Each row contains on points.}
+}
+\value{
+[\code{list}]
+  List with the following components
+  \describe{
+    \item{ranks}{Integer vector of ranks of length \code{nrow(x)}. The higher
+    the rank, the higher the domination front the corresponding points is
+    located on.}
+    \item{dom.counter}{Integer vector of length \code{nrow(x)}. The i-th element
+    is the domination counter / domination number of the i-th point.}
+  }
+}
+\description{
+Implementation of the fast non-dominated sorting algorithm proposed by Deb.
+}
+