stdev.js (1461B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2018 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 sqrt = require( '@stdlib/math/base/special/sqrt' ); 24 25 26 // VARIABLES // 27 28 var SQRT1O12 = sqrt( 1.0/12.0 ); 29 30 31 // MAIN // 32 33 /** 34 * Returns the standard deviation of a uniform distribution. 35 * 36 * @param {number} a - minimum support 37 * @param {number} b - maximum support 38 * @returns {PositiveNumber} standard deviation 39 * 40 * @example 41 * var v = stdev( 0.0, 1.0 ); 42 * // returns ~0.289 43 * 44 * @example 45 * var v = stdev( 4.0, 12.0 ); 46 * // returns ~2.309 47 * 48 * @example 49 * var v = stdev( -4.0, 4.0 ); 50 * // returns ~2.309 51 * 52 * @example 53 * var v = stdev( 1.0, -0.1 ); 54 * // returns NaN 55 * 56 * @example 57 * var v = stdev( 2.0, NaN ); 58 * // returns NaN 59 * 60 * @example 61 * var v = stdev( NaN, 2.0 ); 62 * // returns NaN 63 */ 64 function stdev( a, b ) { 65 if ( 66 a >= b 67 ) { 68 return NaN; 69 } 70 return SQRT1O12 * ( b-a ); 71 } 72 73 74 // EXPORTS // 75 76 module.exports = stdev;