ndarray.js (1649B)
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 // MAIN // 22 23 /** 24 * Computes the arithmetic mean of a strided array, ignoring `NaN` values and using ordinary recursive summation. 25 * 26 * @param {PositiveInteger} N - number of indexed elements 27 * @param {NumericArray} x - input array 28 * @param {integer} stride - stride length 29 * @param {NonNegativeInteger} offset - starting index 30 * @returns {number} arithmetic mean 31 * 32 * @example 33 * var floor = require( '@stdlib/math/base/special/floor' ); 34 * 35 * var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0, NaN ]; 36 * var N = floor( x.length / 2 ); 37 * 38 * var v = nanmeanors( N, x, 2, 1 ); 39 * // returns 1.25 40 */ 41 function nanmeanors( N, x, stride, offset ) { 42 var sum; 43 var ix; 44 var v; 45 var n; 46 var i; 47 48 if ( N <= 0 ) { 49 return NaN; 50 } 51 if ( N === 1 || stride === 0 ) { 52 return x[ offset ]; 53 } 54 ix = offset; 55 sum = 0.0; 56 n = 0; 57 for ( i = 0; i < N; i++ ) { 58 v = x[ ix ]; 59 if ( v === v ) { 60 sum += v; 61 n += 1; 62 } 63 ix += stride; 64 } 65 if ( n === 0 ) { 66 return NaN; 67 } 68 return sum / n; 69 } 70 71 72 // EXPORTS // 73 74 module.exports = nanmeanors;