mean.js (1223B)
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 25 26 // MAIN // 27 28 /** 29 * Returns the expected value of a chi-squared distribution. 30 * 31 * @param {NonNegativeNumber} k - degrees of freedom 32 * @returns {NonNegativeNumber} expected value 33 * 34 * @example 35 * var v = mean( 9.0 ); 36 * // returns 9.0 37 * 38 * @example 39 * var v = mean( 1.0 ); 40 * // returns 1.0 41 * 42 * @example 43 * var v = mean( -0.2 ); 44 * // returns NaN 45 * 46 * @example 47 * var v = mean( NaN ); 48 * // returns NaN 49 */ 50 function mean( k ) { 51 if ( isnan( k ) || k < 0.0 ) { 52 return NaN; 53 } 54 return k; 55 } 56 57 58 // EXPORTS // 59 60 module.exports = mean;