gaussian.js (1342B)
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/assert/is-nan' ); 24 var pow = require( '@stdlib/math/base/special/pow' ); 25 var SQRT_TWO_PI = require( '@stdlib/constants/float64/sqrt-two-pi' ); 26 var exp = require( '@stdlib/math/base/special/exp' ); 27 28 29 // VARIABLES // 30 31 var INV_SQRT_TWO_PI = 1.0 / SQRT_TWO_PI; 32 33 34 // MAIN // 35 36 /** 37 * Computes the Gaussian kernel for a value. 38 * 39 * @private 40 * @param {number} u - input value 41 * @returns {number} the value for the Gaussian kernel at u 42 * 43 * @example 44 * var u = 5.0; 45 * var out = gaussian( u ); 46 * // returns ~0.0 47 */ 48 function gaussian( u ) { 49 if ( isnan( u ) ) { 50 return NaN; 51 } 52 return INV_SQRT_TWO_PI * exp( -0.5 * pow( u, 2.0 ) ); 53 } 54 55 56 // EXPORTS // 57 58 module.exports = gaussian;