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
|
/**
* @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.
*
*
* ## Notice
*
* The original C++ code and copyright notice are from the [Boost library]{@link http://www.boost.org/doc/libs/1_37_0/boost/math/special_functions/gamma.hpp}. The implementation has been modified for JavaScript.
*
* ```text
* (C) Copyright John Maddock 2006.
* (C) Copyright Paul A. Bristow 2007.
*
* Use, modification and distribution are subject to the
* Boost Software License, Version 1.0. (See accompanying file
* LICENSE or copy at http://www.boost.org/LICENSE_1_0.txt)
* ```
*/
'use strict';
// MODULES //
var sumSeries = require( './../../../../base/tools/sum-series' );
var lowerIncompleteGammaSeries = require( './lower_incomplete_gamma_series.js' );
// MAIN //
/**
* Sums elements of the series expansion of the lower incomplete gamma function.
*
* ## Method
*
* - Multiply result by `((z^a) * (e^-z) / a)` to get the full lower incomplete integral.
* - Divide by `tgamma(a)` to get the normalized value.
*
* @private
* @param {number} a - function parameter
* @param {number} z - function parameter
* @param {number} initialValue - initial value of the resulting sum
* @returns {number} sum of terms of lower gamma series
*/
function lowerGammaSeries( a, z, initialValue ) {
var result;
var s;
initialValue = initialValue || 0.0;
s = lowerIncompleteGammaSeries( a, z );
result = sumSeries( s, {
'initialValue': initialValue
});
return result;
}
// EXPORTS //
module.exports = lowerGammaSeries;
|
