R/scale_mad.R

In RemPsyc/rempsyc: Convenience Functions for Psychology

#' @title Standardize based on the absolute median deviation
#'
#' @description Scale and center ("standardize") data based on
#' the median absolute deviation (MAD).
#'
#' @details The function subtracts the median to each observation, and then
#' divides the outcome by the MAD. This is analogous to regular standardization
#' which subtracts the mean to each observaion, and then divides the outcome
#' by the standard deviation.
#'
#' For the *easystats* equivalent, use:
#' `datawizard::standardize(x, robust = TRUE)`.
#'
#' @param x The vector to be scaled.
#' @keywords standardization normalization median MAD mean outliers
#' @return A numeric vector of standardized data.
#' @references Leys, C., Ley, C., Klein, O., Bernard, P., & Licata, L.
#' (2013). Detecting outliers: Do not use standard deviation
#' around the mean, use absolute deviation around the median.
#' *Journal of Experimental Social Psychology*, *49*(4), 764–766.
#' https://doi.org/10.1016/j.jesp.2013.03.013
#' @export
#' @examples
#' scale_mad(mtcars$mpg)
#' @importFrom stats mad median

scale_mad <- function(x) {
  median.x <- median(x, na.rm = TRUE)
  mad.x <- mad(x, na.rm = TRUE)
  y <- (x - median.x) / mad.x
  y
}