R/moda.R

In elpidiofilho/mdsFuncs: Auxiliar functions to pre-process raster data and modelling with machine learning models using caret package

#' Frequency of modal values
#' @description Calculates the frequency of occurrence of the
#'     modal value for each cell/pixel of a raster stack
#' @param r SpatRaster
#' @param ncores integer number of cores for multiprocessing
#' @author <elpidio@ufv.br>
#' @return SpatRaster
#' @export
#' @importFrom terra app
#' @examples
#' # modalfreq = mode_freq(r = r1, ncores = 2)
mode_freq <- function(r, ncores = 2) {
  if (class(r) == "RasterStack") {
    r <- rast(r)
  } else {
    if (class(r) != "SpatRaster") {
      stop("Error : file must be in RasterStack or SpatRaster format")
    }
  }
  if (is.na(terra::crs(r))) {
    stop("r does not have a coordinate system")
  }
  Mode_count <- function(x) {
    ux <- unique(x)
    ux <- ux[!is.na(ux)]
    mode <- ux[which.max(tabulate(match(x, ux)))]
    mc <- sum(x == mode, na.rm = TRUE)
    return(mc)
  }
  freq <- terra::app(r, fun = Mode_count, cores = ncores)
  return(freq)
}