ndarray.js (1861B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2020 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 gsumkbn2 = require( '@stdlib/blas/ext/base/gsumkbn2' ).ndarray; 24 25 26 // MAIN // 27 28 /** 29 * Computes the arithmetic mean of a strided array using a second-order iterative Kahan–Babuška algorithm. 30 * 31 * ## Method 32 * 33 * - This implementation uses a second-order iterative Kahan–Babuška algorithm, as described by Klein (2005). 34 * 35 * ## References 36 * 37 * - Klein, Andreas. 2005. "A Generalized Kahan-Babuška-Summation-Algorithm." _Computing_ 76 (3): 279–93. doi:[10.1007/s00607-005-0139-x](https://doi.org/10.1007/s00607-005-0139-x). 38 * 39 * @param {PositiveInteger} N - number of indexed elements 40 * @param {NumericArray} x - input array 41 * @param {integer} stride - stride length 42 * @param {NonNegativeInteger} offset - starting index 43 * @returns {number} arithmetic mean 44 * 45 * @example 46 * var floor = require( '@stdlib/math/base/special/floor' ); 47 * 48 * var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ]; 49 * var N = floor( x.length / 2 ); 50 * 51 * var v = meankbn2( N, x, 2, 1 ); 52 * // returns 1.25 53 */ 54 function meankbn2( N, x, stride, offset ) { 55 if ( N <= 0 ) { 56 return NaN; 57 } 58 if ( N === 1 || stride === 0 ) { 59 return x[ offset ]; 60 } 61 return gsumkbn2( N, x, stride, offset ) / N; 62 } 63 64 65 // EXPORTS // 66 67 module.exports = meankbn2;