ndarray.js (1717B)
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 floor = require( '@stdlib/math/base/special/floor' ); 24 25 26 // MAIN // 27 28 /** 29 * Computes the median value of a sorted double-precision floating-point strided array. 30 * 31 * @param {PositiveInteger} N - number of indexed elements 32 * @param {Float64Array} x - sorted input array 33 * @param {integer} stride - stride length 34 * @param {NonNegativeInteger} offset - starting index 35 * @returns {number} median value 36 * 37 * @example 38 * var Float64Array = require( '@stdlib/array/float64' ); 39 * var floor = require( '@stdlib/math/base/special/floor' ); 40 * 41 * var x = new Float64Array( [ 2.0, -3.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] ); 42 * var N = floor( x.length / 2 ); 43 * 44 * var v = dmediansorted( N, x, 2, 1 ); 45 * // returns 0.0 46 */ 47 function dmediansorted( N, x, stride, offset ) { 48 var n; 49 var m; 50 51 if ( N <= 0 ) { 52 return NaN; 53 } 54 n = N / 2; 55 m = floor( n ); 56 if ( n === m ) { 57 // Even number of elements... 58 return ( x[ offset+(m*stride) ] + x[ offset+((m-1)*stride) ] ) / 2.0; 59 } 60 // Odd number of elements... 61 return x[ offset+(m*stride) ]; 62 } 63 64 65 // EXPORTS // 66 67 module.exports = dmediansorted;