mean.js (1566B)
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 isnan = require( '@stdlib/math/base/assert/is-nan' ); 24 var isInteger = require( '@stdlib/math/base/assert/is-integer' ); 25 26 27 // MAIN // 28 29 /** 30 * Returns the expected value of a discrete uniform distribution. 31 * 32 * @param {integer} a - minimum support 33 * @param {integer} b - maximum support 34 * @returns {number} expected value 35 * 36 * @example 37 * var v = mean( 0, 1 ); 38 * // returns 0.5 39 * 40 * @example 41 * var v = mean( -4, 4 ); 42 * // returns 0.0 43 * 44 * @example 45 * var v = mean( 0, 10 ); 46 * // returns 5.0 47 * 48 * @example 49 * var v = mean( 1, -0.1 ); 50 * // returns NaN 51 * 52 * @example 53 * var v = mean( -0.1, 1 ); 54 * // returns NaN 55 * 56 * @example 57 * var v = mean( 2, NaN ); 58 * // returns NaN 59 * 60 * @example 61 * var v = mean( NaN, 2 ); 62 * // returns NaN 63 */ 64 function mean( a, b ) { 65 if ( 66 isnan( a ) || 67 isnan( b ) || 68 !isInteger( a ) || 69 !isInteger( b ) || 70 a > b 71 ) { 72 return NaN; 73 } 74 return ( a/2 ) + ( b/2 ); 75 } 76 77 78 // EXPORTS // 79 80 module.exports = mean;