ndarray.js (2253B)
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 float64ToFloat32 = require( '@stdlib/number/float64/base/to-float32' ); 24 var svariancewd = require( './../../../base/svariancewd' ).ndarray; 25 var sqrt = require( '@stdlib/math/base/special/sqrt' ); 26 27 28 // MAIN // 29 30 /** 31 * Computes the standard deviation of a single-precision floating-point strided array using Welford's algorithm. 32 * 33 * ## References 34 * 35 * - Welford, B. P. 1962. "Note on a Method for Calculating Corrected Sums of Squares and Products." _Technometrics_ 4 (3). Taylor & Francis: 419–20. doi:[10.1080/00401706.1962.10490022](https://doi.org/10.1080/00401706.1962.10490022). 36 * - van Reeken, A. J. 1968. "Letters to the Editor: Dealing with Neely's Algorithms." _Communications of the ACM_ 11 (3): 149–50. doi:[10.1145/362929.362961](https://doi.org/10.1145/362929.362961). 37 * 38 * @param {PositiveInteger} N - number of indexed elements 39 * @param {number} correction - degrees of freedom adjustment 40 * @param {Float32Array} x - input array 41 * @param {integer} stride - stride length 42 * @param {NonNegativeInteger} offset - starting index 43 * @returns {number} standard deviation 44 * 45 * @example 46 * var Float32Array = require( '@stdlib/array/float32' ); 47 * var floor = require( '@stdlib/math/base/special/floor' ); 48 * 49 * var x = new Float32Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] ); 50 * var N = floor( x.length / 2 ); 51 * 52 * var v = sstdevwd( N, 1, x, 2, 1 ); 53 * // returns 2.5 54 */ 55 function sstdevwd( N, correction, x, stride, offset ) { 56 return float64ToFloat32( sqrt( svariancewd( N, correction, x, stride, offset ) ) ); // eslint-disable-line max-len 57 } 58 59 60 // EXPORTS // 61 62 module.exports = sstdevwd;