nanmeanors.js (1534B)
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 * @returns {number} arithmetic mean 30 * 31 * @example 32 * var x = [ 1.0, -2.0, NaN, 2.0 ]; 33 * var N = x.length; 34 * 35 * var v = nanmeanors( N, x, 1 ); 36 * // returns ~0.3333 37 */ 38 function nanmeanors( N, x, stride ) { 39 var sum; 40 var ix; 41 var v; 42 var n; 43 var i; 44 45 if ( N <= 0 ) { 46 return NaN; 47 } 48 if ( N === 1 || stride === 0 ) { 49 return x[ 0 ]; 50 } 51 if ( stride < 0 ) { 52 ix = (1-N) * stride; 53 } else { 54 ix = 0; 55 } 56 sum = 0.0; 57 n = 0; 58 for ( i = 0; i < N; i++ ) { 59 v = x[ ix ]; 60 if ( v === v ) { 61 sum += v; 62 n += 1; 63 } 64 ix += stride; 65 } 66 if ( n === 0 ) { 67 return NaN; 68 } 69 return sum / n; 70 } 71 72 73 // EXPORTS // 74 75 module.exports = nanmeanors;