poisson.js (1194B)
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 knuth = require( './knuth.js' ); 24 var rejection = require( './rejection.js' ); 25 26 27 // MAIN // 28 29 /** 30 * Returns a pseudorandom number drawn from a Poisson distribution with parameter `lambda`. 31 * 32 * @private 33 * @param {PRNG} rand - PRNG for generating uniformly distributed numbers 34 * @param {PositiveNumber} lambda - mean 35 * @returns {NonNegativeInteger} pseudorandom number 36 */ 37 function poisson( rand, lambda ) { 38 if ( lambda < 30.0 ) { 39 return knuth( rand, lambda ); 40 } 41 return rejection( rand, lambda ); 42 } 43 44 45 // EXPORTS // 46 47 module.exports = poisson;