R/mutator.rotation.R

In jakobbossek/tspgen: Problem Generator for Traveling Salesperson Problems

#' @title Rotation mutation
#'
#' @description
#' A subset \eqn{Q \subseteq P} of the points is selected and rotated
#' by a randomly sampled angle around its center.
#
#' @template arg_coords
#' @template arg_pm
#' @template arg_dots
#' @return [\code{matrix}] Mutated coordinates.
#' @family mutation operators
#' @seealso \code{\link{build}}
#' @export
doRotationMutation = function(coords, pm = 0.1, ...) {
  checkmate::assertMatrix(coords, ncols = 2L, mode = "numeric", any.missing = FALSE, all.missing = FALSE)
  checkmate::assertNumber(pm, lower = 0, upper = 1)

  to.mutate = sampleRows(coords, p = pm)
  angle = stats::runif(1L, min = 0, max = 360)
  rot.mat = getRotationMatrix(angle)

  if (length(to.mutate) < 2L)
    return(coords)

  # NOTE: rotation is centered around origin. Hence, we shift the rotated point cloud by a random number
  mutants = t(rot.mat %*% t(coords[to.mutate, ]) + stats::runif(2L))
  #coords[to.mutate, ] = forceToBounds(mutants)
  coords[to.mutate, ] = mutants

  if (!is.null(getOption("tspgen.debug")))
    attr(coords, "df") = mutationAsDataframe(coords, to.mutate)

  return(coords)
}