absdiff.js (1873B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2021 The Stdlib Authors. 5 * 6 * Licensed under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 'use strict'; 20 21 // MODULES // 22 23 var incrmean = require( './../../incr/mean' ); 24 var abs = require( '@stdlib/math/base/special/abs' ); 25 26 27 // MAIN // 28 29 /** 30 * Calculates the absolute difference of the values and the respective group means for the elements of a numeric array. 31 * 32 * @private 33 * @param {Array} x - input array 34 * @param {Array} groups - array of group labels 35 * @param {Array} levels - array of distinct group levels 36 * @returns {Array} array of absolute centered values 37 * 38 * @example 39 * var x = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]; 40 * var groups = [ 'a', 'b', 'a', 'a', 'b', 'b', 'a', 'a', 'b', 'b' ]; 41 * var levels = [ 'a', 'b' ]; 42 * var out = absMeanDiff( x, groups, levels ); 43 * // returns [ ~3.6, 4.4, ..., ~3.6 ] 44 */ 45 function absMeanDiff( x, groups, levels ) { 46 var accumulators = {}; 47 var means = {}; 48 var len = x.length; 49 var out = []; 50 var i; 51 for ( i = 0; i < levels.length; i++ ) { 52 accumulators[ levels[ i ] ] = incrmean(); 53 } 54 for ( i = 0; i < len; i++ ) { 55 accumulators[ groups[ i ] ]( x[ i ] ); 56 } 57 for ( i = 0; i < levels.length; i++ ) { 58 means[ levels[ i ] ] = accumulators[ levels[ i ] ](); 59 } 60 for ( i = 0; i < len; i++ ) { 61 out.push( abs( x[ i ] - means[ groups[ i ] ] ) ); 62 } 63 return out; 64 } 65 66 67 // EXPORTS // 68 69 module.exports = absMeanDiff;