factory.js (1695B)
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 constantFunction = require( '@stdlib/utils/constant-function' ); 24 var isnan = require( '@stdlib/math/base/assert/is-nan' ); 25 26 27 // MAIN // 28 29 /** 30 * Returns a function for evaluating the cumulative distribution function (CDF) for a Bernoulli distribution with success probability `p`. 31 * 32 * @param {Probability} p - success probability 33 * @returns {Function} CDF 34 * 35 * @example 36 * var cdf = factory( 0.5 ); 37 * var y = cdf( 3.0 ); 38 * // returns 1.0 39 * 40 * y = cdf( 0.7 ); 41 * // returns 0.5 42 */ 43 function factory( p ) { 44 if ( isnan( p ) || p < 0.0 || p > 1.0 ) { 45 return constantFunction( NaN ); 46 } 47 return cdf; 48 49 /** 50 * Evaluates the cumulative distribution function (CDF) for a Bernoulli distribution. 51 * 52 * @private 53 * @param {number} x - input value 54 * @returns {Probability} evaluated CDF 55 * 56 * @example 57 * var y = cdf( 2.0 ); 58 * // returns <number> 59 */ 60 function cdf( x ) { 61 if ( isnan( x ) ) { 62 return NaN; 63 } 64 if ( x < 0.0 ) { 65 return 0.0; 66 } 67 if ( x >= 1.0 ) { 68 return 1.0; 69 } 70 return 1.0 - p; 71 } 72 } 73 74 75 // EXPORTS // 76 77 module.exports = factory;