beta.js (1495B)
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 sample1 = require( './sample1.js' ); 24 var sample2 = require( './sample2.js' ); 25 var sample3 = require( './sample3.js' ); 26 27 28 // MAIN // 29 30 /** 31 * Returns a random number drawn from a beta distribution. 32 * 33 * @private 34 * @param {PRNG} randu - pseudorandom number generator for uniformly distributed numbers 35 * @param {PRNG} randn - pseudorandom number generator for normally distributed numbers 36 * @param {PositiveNumber} alpha - first shape parameter 37 * @param {PositiveNumber} beta - second shape parameter 38 * @returns {Probability} pseudorandom number 39 */ 40 function sample( randu, randn, alpha, beta ) { 41 if ( alpha === beta && alpha > 1.5 ) { 42 return sample1( randu, randn, alpha ); 43 } 44 if ( alpha > 1.0 && beta > 1.0 ) { 45 return sample2( randu, randn, alpha, beta ); 46 } 47 return sample3( randu, alpha, beta ); 48 } 49 50 51 // EXPORTS // 52 53 module.exports = sample;