mlcc.kmeans.R

#' Multiple Latent Components Clustering - kmeans algorithm
#'
#' Performs k-means based subspace clustering. Center of each cluster is some
#' number of principal components. This number can be fixed or estimated by
#' PESEL. Similarity measure between variable and a cluster is calculated using
#' BIC.
#'
#' @param X A matrix with only continuous variables.
#' @param number.clusters An integer, number of clusters to be used.
#' @param stop.criterion An integer indicating how many changes in partitions
#'   triggers stopping the algorithm.
#' @param max.iter An integer, maximum number of iterations of k-means loop.
#' @param max.subspace.dim An integer, maximum dimension of subspaces.
#' @param initial.segmentation A vector, initial segmentation of variables to
#'   clusters.
#' @param estimate.dimensions A boolean, if TRUE (value set by default)
#'   subspaces dimensions are estimated.
#' @param show.warnings A boolean, if set to TRUE all warnings are displayed,
#'   default value is FALSE.
#' @references \emph{Bayesian dimensionality reduction with PCA using penalized semi-integrated likelihood},
#' Piotr Sobczyk, Malgorzata Bogdan, Julie Josse
#' @export
#' @return A list consisting of: \item{segmentation}{a vector containing the
#'   partition of the variables} \item{pcas}{a list of matrices, basis vectors
#'   for each cluster (subspace)}
#' @examples
#' \donttest{
#' sim.data <- data.simulation(n = 50, SNR = 1, K = 5, numb.vars = 50, max.dim = 3)
#' mlcc.res <- mlcc.kmeans(sim.data$X, number.clusters = 5, max.iter = 20, max.subspace.dim = 3)
#' show.clusters(sim.data$X, mlcc.res$segmentation)
#' }
mlcc.kmeans <- function(X, number.clusters = 2, stop.criterion = 1, max.iter = 30,
                        max.subspace.dim = 4, initial.segmentation = NULL, estimate.dimensions = TRUE,
                        show.warnings = FALSE) {
  numbVars <- dim(X)[2]
  rowNumb <- dim(X)[1]
  if (!is.null(initial.segmentation) && length(initial.segmentation) != numbVars) {
    stop(paste(
      "The lenght of initial segmentation was incorrect: ", length(initial.segmentation),
      ".It should be: ", numbVars
    ))
  }
  if (!is.null(initial.segmentation) && max(initial.segmentation) > number.clusters) {
    stop(paste("Too many cluster indices in initial segmentation. Should be in range [1, number.clusters]."))
  }
  pcas <- list(NULL)

  if (is.null(initial.segmentation)) {
    los <- sample(1:numbVars, number.clusters)
    pcas <- lapply(1:number.clusters, function(i) matrix(X[, los[i]], nrow = rowNumb))
    segmentation <- sapply(1:numbVars, function(j) {
      choose.cluster.BIC(
        X[, j],
        pcas, number.clusters, show.warnings
      )
    })
  } else {
    segmentation <- initial.segmentation
  }

  new.segmentation <- segmentation
  for (iter in 1:max.iter) {
    pcas <- calculate.pcas(
      X, segmentation, number.clusters, max.subspace.dim,
      estimate.dimensions
    )
    new.segmentation <- sapply(1:numbVars, function(j) {
      choose.cluster.BIC(X[
        ,
        j
      ], pcas, number.clusters, show.warnings)
    })
    if (sum(new.segmentation != segmentation) < stop.criterion) {
      break
    }
    segmentation <- new.segmentation
  }
  pcas <- calculate.pcas(X, segmentation, number.clusters, max.subspace.dim, estimate.dimensions)
  return(list(segmentation = segmentation, pcas = pcas))
}