factory.js (2507B)
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 isNonNegativeInteger = require( '@stdlib/math/base/assert/is-nonnegative-integer' ); 24 var isnan = require( '@stdlib/math/base/assert/is-nan' ); 25 var constantFunction = require( '@stdlib/utils/constant-function' ); 26 var max = require( '@stdlib/math/base/special/max' ); 27 var min = require( '@stdlib/math/base/special/min' ); 28 var cdf = require( './../../../../../base/dists/hypergeometric/cdf' ); 29 var PINF = require( '@stdlib/constants/float64/pinf' ); 30 31 32 // MAIN // 33 34 /** 35 * Returns a function for evaluating the quantile function for a hypergeometric distribution with population size `N`, subpopulation size `K`, and number of draws `n`. 36 * 37 * @param {NonNegativeInteger} N - population size 38 * @param {NonNegativeInteger} K - subpopulation size 39 * @param {NonNegativeInteger} n - number of draws 40 * @returns {Function} quantile function 41 * 42 * @example 43 * var quantile = factory( 100, 20, 10 ); 44 * var y = quantile( 0.2 ); 45 * // returns 1 46 * 47 * y = quantile( 0.9 ); 48 * // returns 4 49 */ 50 function factory( N, K, n ) { 51 if ( 52 isnan( N ) || 53 isnan( K ) || 54 isnan( n ) || 55 !isNonNegativeInteger( N ) || 56 !isNonNegativeInteger( K ) || 57 !isNonNegativeInteger( n ) || 58 N === PINF || 59 K === PINF || 60 K > N || 61 n > N 62 ) { 63 return constantFunction( NaN ); 64 } 65 return quantile; 66 67 /** 68 * Evaluates the quantile function for a hypergeometric distribution. 69 * 70 * @private 71 * @param {Probability} p - input value 72 * @returns {NonNegativeInteger} evaluated quantile function 73 */ 74 function quantile( p ) { 75 var prob; 76 var x; 77 78 if ( isnan( p ) || p < 0.0 || p > 1.0 ) { 79 return NaN; 80 } 81 if ( p === 0.0 ) { 82 return max( 0, n + K - N ); 83 } 84 if ( p === 1.0 ) { 85 return min( n, K ); 86 } 87 x = max( 0, n + K - N ); 88 while ( true ) { 89 prob = cdf( x, N, K, n ); 90 if ( prob > p ) { 91 break; 92 } 93 x += 1; 94 } 95 return x; 96 } 97 } 98 99 100 // EXPORTS // 101 102 module.exports = factory;