randomIndex.ts

// Copyright (c) 2022 Onur Cinar. All Rights Reserved.
// https://github.com/cinar/indicatorts

import { divide, multiplyBy, subtract } from '../../helper/numArray';
import { mmin } from './movingMin';
import { mmax } from './movingMax';
import { sma } from './simpleMovingAverage';

/**
 * KDJ result.
 */
export interface KDJResult {
  k: number[];
  d: number[];
  j: number[];
}

/**
 * Optional configuration of KDJ parameters.
 */
export interface KDJConfig {
  rPeriod?: number;
  kPeriod?: number;
  dPeriod?: number;
}

/**
 * The default configuration of KDJ.
 */
export const KDJDefaultConfig: Required<KDJConfig> = {
  rPeriod: 9,
  kPeriod: 3,
  dPeriod: 3,
};

/**
 * The kdj function calculates the KDJ indicator, also known as
 * the Random Index. KDJ is calculated similar to the Stochastic
 * Oscillator with the difference of having the J line. It is
 * used to analyze the trend and entry points.
 *
 * The K and D lines show if the asset is overbought when they
 * crosses above 80%, and oversold when they crosses below
 * 20%. The J line represents the divergence.
 *
 * RSV = ((Closing - Min(Low, rPeriod))
 *       / (Max(High, rPeriod) - Min(Low, rPeriod))) * 100
 * K = Sma(RSV, kPeriod)
 * D = Sma(K, dPeriod)
 * J = (3 * K) - (2 * D)
 *
 * @param highs high values.
 * @param lows low values.
 * @param closings closing values.
 * @param config configuration.
 * @return kdj result.
 */
export function kdj(
  highs: number[],
  lows: number[],
  closings: number[],
  config: KDJConfig = {}
): KDJResult {
  const { rPeriod, kPeriod, dPeriod } = { ...KDJDefaultConfig, ...config };
  const highest = mmax(highs, { period: rPeriod });
  const lowest = mmin(lows, { period: rPeriod });

  const rsv = multiplyBy(
    100,
    divide(subtract(closings, lowest), subtract(highest, lowest))
  );

  const kValue = sma(rsv, { period: kPeriod });
  const dValue = sma(kValue, { period: dPeriod });
  const jValue = subtract(multiplyBy(3, kValue), multiplyBy(2, dValue));

  return {
    k: kValue,
    d: dValue,
    j: jValue,
  };
}

// Export full name
export { kdj as randomIndex };