Developer documentation Version 3.0.3-105-gd3941f44
welch_satterthwaite.h
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1/* Copyright (c) 2008-2022 the MRtrix3 contributors.
2 *
3 * This Source Code Form is subject to the terms of the Mozilla Public
4 * License, v. 2.0. If a copy of the MPL was not distributed with this
5 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
6 *
7 * Covered Software is provided under this License on an "as is"
8 * basis, without warranty of any kind, either expressed, implied, or
9 * statutory, including, without limitation, warranties that the
10 * Covered Software is free of defects, merchantable, fit for a
11 * particular purpose or non-infringing.
12 * See the Mozilla Public License v. 2.0 for more details.
13 *
14 * For more details, see http://www.mrtrix.org/.
15 */
16
17#ifndef __math_welch_satterthwaite_h__
18#define __math_welch_satterthwaite_h__
19
20#include "math/math.h"
21
22namespace MR {
23 namespace Math {
24
25
26
27 template <class VarArrayType, class CountArrayType>
28 default_type welch_satterthwaite (const VarArrayType& variances, const CountArrayType& counts)
29 {
30 assert (size_t(variances.size()) == size_t(counts.size()));
31 default_type numerator = 0.0, denominator = 0.0;
32 for (size_t i = 0; i != size_t(variances.size()); ++i) {
33 const default_type ks2 = (1.0 / (counts[i] - 1)) * variances[i];
34 numerator += ks2;
35 denominator += Math::pow2 (ks2) / (counts[i] - 1);
36 }
37 return Math::pow2 (numerator) / denominator;
38 }
39
40
41
42 }
43}
44
45#endif
constexpr T pow2(const T &v)
Definition: math.h:53
default_type welch_satterthwaite(const VarArrayType &variances, const CountArrayType &counts)
Definition: base.h:24
double default_type
the default type used throughout MRtrix
Definition: types.h:228