Press n or j to go to the next uncovered block, b, p or k for the previous block.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 | 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 2x 3027x 3027x 3027x 3027x 3027x 3027x 3027x 3016x 3027x 15x 15x 3027x 6x 6x 6x 3027x 3x 1x 1x 3x 1x 1x 1x 1x 3027x 3x 1x 1x 3x 1x 1x 1x 1x 3000x 3000x 3000x 3000x 3027x 2x 2x 2x 2x 2x | /**
* @license Apache-2.0
*
* Copyright (c) 2018 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
// MODULES //
var betaln = require( '@stdlib/math/base/special/betaln' );
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var log1p = require( '@stdlib/math/base/special/log1p' );
var exp = require( '@stdlib/math/base/special/exp' );
var ln = require( '@stdlib/math/base/special/ln' );
var PINF = require( '@stdlib/constants/float64/pinf' );
// MAIN //
/**
* Evaluates the probability density function (PDF) for a beta distribution with first shape parameter `alpha` and second shape parameter `beta` at a value `x`.
*
* @param {number} x - input value
* @param {PositiveNumber} alpha - first shape parameter
* @param {PositiveNumber} beta - second shape parameter
* @returns {number} evaluated PDF
*
* @example
* var y = pdf( 0.5, 1.0, 1.0 );
* // returns 1.0
*
* @example
* var y = pdf( 0.5, 2.0, 4.0 );
* // returns 1.25
*
* @example
* var y = pdf( 0.2, 2.0, 2.0 );
* // returns ~0.96
*
* @example
* var y = pdf( 0.8, 4.0, 4.0 );
* // returns ~0.573
*
* @example
* var y = pdf( -0.5, 4.0, 2.0 );
* // returns 0.0
*
* @example
* var y = pdf( 1.5, 4.0, 2.0 );
* // returns 0.0
*
* @example
* var y = pdf( 0.5, -1.0, 0.5 );
* // returns NaN
*
* @example
* var y = pdf( 0.5, 0.5, -1.0 );
* // returns NaN
*
* @example
* var y = pdf( NaN, 1.0, 1.0 );
* // returns NaN
*
* @example
* var y = pdf( 0.5, NaN, 1.0 );
* // returns NaN
*
* @example
* var y = pdf( 0.5, 1.0, NaN );
* // returns NaN
*/
function pdf( x, alpha, beta ) {
var out;
if (
isnan( x ) ||
isnan( alpha ) ||
isnan( beta ) ||
alpha <= 0.0 ||
beta <= 0.0
) {
return NaN;
}
if ( x < 0.0 || x > 1.0 ) {
// Support of the Beta distribution: [0,1]
return 0.0;
}
if ( x === 0.0 ) {
if ( alpha < 1.0 ) {
return PINF;
}
if ( alpha > 1.0 ) {
return 0.0;
}
return beta;
}
if ( x === 1.0 ) {
if ( beta < 1.0 ) {
return PINF;
}
if ( beta > 1.0 ) {
return 0.0;
}
return alpha;
}
out = ( alpha-1.0 ) * ln( x );
out += ( beta-1.0 ) * log1p( -x );
out -= betaln( alpha, beta );
return exp( out );
}
// EXPORTS //
module.exports = pdf;
|