code: function MADMeanRatio(actuals, estimates) {
    const MAD = meanAbsoluteDeviation(actuals, estimates);
    const mean = avg(actuals);
    return MAD / mean;
  }
docs: MAD over Mean Ratio - The MAD/Mean ratio is an alternative to the MAPE that is better suited to intermittent and low-volume data. As stated previously, percentage errors cannot be calculated when the actual equals zero and can take on extreme values when dealing with low-volume data. These issues become magnified when you start to average MAPEs over multiple time series. The MAD/Mean ratio tries to overcome this problem by dividing the MAD by the Mean—essentially rescaling the error to make it comparable across time series of varying scales
  @memberOf util
  @see {@link https://www.forecastpro.com/Trends/forecasting101August2011.html}
  @example
  const actuals = [ 45, 38, 43, 39 ];
  const estimates = [ 41, 43, 41, 42 ];
  const MMR = ms.util.MADMeanRatio(actuals, estimates);
  MAPE.toFixed(2) // => 0.08
  @param {Number[]} actuals - numerical samples
  @param {Number[]} estimates - estimates values
  @returns {Number} MMR