maia-util/dist/sample_without_replacement.js

Utility math and music functions supporting various applications by Music Artificial Intelligence Algorithms, Inc.

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = sample_without_replacement;

var _get_random_int = require('./get_random_int');

var _get_random_int2 = _interopRequireDefault(_get_random_int);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

/**
 * This function returns a random sample of elements from an input array, where
 * the sampling is without replacement.
 *
 * @author Tom Collins
 * @comment 30th June 2019
 * @param {Array<number|string|boolean>} arr - Input array
 * @param {number} sampleSize - Size of requested sample
 * @return {Array<number|string|boolean>} Output array
 *
 * @example
 *     sample_without_replacement(["a", "b", "c"], 2);
 * →
 * ["c", "a"]
 */
function sample_without_replacement(arr, sampleSize) {
  var n = arr.length;
  if (n > 0) {
    if (n >= sampleSize) {
      var idxUnchosen = new Array(n);
      for (var i = 0; i < n; i++) {
        idxUnchosen[i] = i;
      }
      // console.log("idxUnchosen:", idxUnchosen);
      var idxChosen = [];
      while (idxChosen.length < sampleSize) {
        // Choose one of the idxUnchosen.
        var idxChoice = (0, _get_random_int2.default)(0, idxUnchosen.length);
        // console.log("idxChoice:", idxChoice);
        // Add it to idxChosen.
        idxChosen.push(idxUnchosen[idxChoice]);
        // console.log("idxChosen:", idxChosen);
        // Remove it from idxUnchosen.
        idxUnchosen.splice(idxChoice, 1);
        // console.log("idxUnchosen:", idxUnchosen);
      }
      return idxChosen.map(function (idx) {
        return arr[idx];
      });
    }
  }
}