betaprime.js (1111B)
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 // MAIN // 22 23 /** 24 * Returns a random number drawn from a beta prime distribution. 25 * 26 * @private 27 * @param {PRNG} rgamma - pseudorandom number generator for gamma distributed numbers 28 * @param {PositiveNumber} alpha - first shape parameter 29 * @param {PositiveNumber} beta - second shape parameter 30 * @returns {PositiveNumber} pseudorandom number 31 */ 32 function sample( rgamma, alpha, beta ) { 33 return rgamma( alpha, 1.0 ) / rgamma( beta, 1.0 ); 34 } 35 36 37 // EXPORTS // 38 39 module.exports = sample;