talisman/metrics/minkowski.js

Straightforward fuzzy matching, information retrieval and NLP building blocks for JavaScript.

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = minkowski;
/**
 * Talisman metrics/minkowski
 * ===========================
 *
 * Function computing the Minkowski distance.
 *
 * [Reference]: https://en.wikipedia.org/wiki/Minkowski_distance
 *
 * [Tags]: metric, vector space.
 */

/**
 * Function returning the Minkowski distance between two vectors.
 *
 * @param  {number} p     - The value for p.
 * @param  {mixed}  a     - The first vector.
 * @param  {mixed}  b     - The second vector.
 * @return {number}       - The Minkowski distance between a & b.
 *
 * @throw  {Error} The function expects a p value >= 1.
 * @throws {Error} The function expects vectors of same dimension.
 */
function minkowski(p, a, b) {
  if (p < 1) throw Error('talisman/metrics/distance/minkowski: the given p-value should be >= 1.');

  if (a.length !== b.length) throw Error('talisman/metrics/distance/minkowski: the given vectors are not of the same dimension.');

  var sum = 0;

  for (var i = 0, l = a.length; i < l; i++) {
    sum += Math.pow(Math.abs(a[i] - b[i]), p);
  }return Math.pow(sum, 1 / p);
}
module.exports = exports['default'];