import type { NumberArray } from 'cheminfo-types';

import { xMedian } from './xMedian.ts';

export interface XMedianAbsoluteDeviationResult {
  /**
   * Median of the data
   */
  median: number;

  /**
   * Median absolute devication
   */
  mad: number;
}

/**
 * This function calculates the median absolute deviation (MAD).
 * https://en.wikipedia.org/wiki/Median_absolute_deviation
 * @param array
 */
export function xMedianAbsoluteDeviation(
  array: NumberArray,
): XMedianAbsoluteDeviationResult {
  const median = xMedian(array);
  const averageDeviations = new Float64Array(array.length);
  for (let i = 0; i < array.length; i++) {
    averageDeviations[i] = Math.abs(array[i] - median);
  }
  return {
    median,
    mad: xMedian(averageDeviations),
  };
}