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/* Copyright (c) 2008-2022 the MRtrix3 contributors.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* Covered Software is provided under this License on an "as is"
* basis, without warranty of any kind, either expressed, implied, or
* statutory, including, without limitation, warranties that the
* Covered Software is free of defects, merchantable, fit for a
* particular purpose or non-infringing.
* See the Mozilla Public License v. 2.0 for more details.
*
* For more details, see http://www.mrtrix.org/.
*/
#ifndef __math_Sn_scale_estimator_h__
#define __math_Sn_scale_estimator_h__
#include "types.h"
#include "math/median.h"
namespace MR {
namespace Math {
// Sn robust estimator of scale to get solid estimate of standard deviation:
// for details, see: Rousseeuw PJ, Croux C. Alternatives to the Median Absolute Deviation. Journal of the American Statistical Association 1993;88:1273–1283.
template <typename value_type = default_type>
class Sn_scale_estimator { NOMEMALIGN
public:
template <class VectorType>
value_type operator() (const VectorType& vec)
{
diff.resize (vec.size());
med_diff.resize (vec.size());
for (ssize_t j = 0; j < vec.size(); ++j) {
for (ssize_t i = 0; i < vec.size(); ++i)
diff[i] = abs (vec[i] - vec[j]);
med_diff[j] = Math::median (diff);
}
return 1.1926 * Math::median (med_diff);
}
protected:
vector<value_type> diff, med_diff;
};
}
}
#endif
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