dnanmeanpw.js (1778B)
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 mean = require( './ndarray.js' ); 24 25 26 // MAIN // 27 28 /** 29 * Computes the arithmetic mean of a double-precision floating-point strided array, ignoring `NaN` values and using pairwise summation. 30 * 31 * @param {PositiveInteger} N - number of indexed elements 32 * @param {Float64Array} x - input array 33 * @param {integer} stride - stride length 34 * @returns {number} arithmetic mean 35 * 36 * @example 37 * var Float64Array = require( '@stdlib/array/float64' ); 38 * 39 * var x = new Float64Array( [ 1.0, -2.0, NaN, 2.0 ] ); 40 * var N = x.length; 41 * 42 * var v = dnanmeanpw( N, x, 1 ); 43 * // returns ~0.3333 44 */ 45 function dnanmeanpw( N, x, stride ) { 46 var ix; 47 var v; 48 var s; 49 var n; 50 var i; 51 52 if ( N <= 0 ) { 53 return NaN; 54 } 55 if ( N === 1 || stride === 0 ) { 56 return x[ 0 ]; 57 } 58 if ( stride < 0 ) { 59 ix = (1-N) * stride; 60 } else { 61 ix = 0; 62 } 63 if ( N < 8 ) { 64 // Use simple summation... 65 s = 0.0; 66 n = 0; 67 for ( i = 0; i < N; i++ ) { 68 v = x[ ix ]; 69 if ( v === v ) { 70 s += v; 71 n += 1; 72 } 73 ix += stride; 74 } 75 if ( n === 0 ) { 76 return NaN; 77 } 78 return s / n; 79 } 80 return mean( N, x, stride, ix ); 81 } 82 83 84 // EXPORTS // 85 86 module.exports = dnanmeanpw;