binomial.js (1267B)
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 26 27 // MAIN // 28 29 /** 30 * Returns a pseudorandom number drawn from a binomial distribution. 31 * 32 * @private 33 * @param {PRNG} rand - PRNG for uniformly distributed numbers 34 * @param {PositiveInteger} n - number of trials 35 * @param {Probability} p - probability of success 36 * @returns {NonNegativeInteger} pseudorandom number 37 */ 38 function sample( rand, n, p ) { 39 if ( p > 0.5 ) { 40 return n - sample( rand, n, 1.0-p ); 41 } 42 if ( n*p < 10.0 ) { 43 return sample1( rand, n, p ); 44 } 45 return sample2( rand, n, p ); 46 } 47 48 49 // EXPORTS // 50 51 module.exports = sample;