ZScoreCalculator.h

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// # Copyright (C) 2000,2001
// # Associated Universities, Inc. Washington DC, USA.
// #
// # This library is free software; you can redistribute it and/or modify it
// # under the terms of the GNU Library General Public License as published by
// # the Free Software Foundation; either version 2 of the License, or (at your
// # option) any later version.
// #
// # This library is distributed in the hope that it will be useful, but WITHOUT
// # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
// # License for more details.
// #
// # You should have received a copy of the GNU Library General Public License
// # along with this library; if not, write to the Free Software Foundation,
// # Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
// #
// # Correspondence concerning AIPS++ should be addressed as follows:
// #        Internet email: casa-feedback@nrao.edu.
// #        Postal address: AIPS++ Project Office
// #                        National Radio Astronomy Observatory
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#ifndef SCIMATH_ZSCORECALCULATOR_H
#define SCIMATH_ZSCORECALCULATOR_H
 
#include <casacore/casa/aips.h>
 
#include <cmath>
#include <map>
#include <mutex>
#include <set>
 
namespace casacore {
 
class Mutex;
 
// This class contains static methods related to z-scores. A z-score is the
// number of standard deviations from the mean in a normal distribution.
 
class ZScoreCalculator {
 public:
  ZScoreCalculator() = delete;
 
  // compute the maximum expected zscore given the number of points
  // in a sample.
  static Double getMaxZScore(uInt64 npts);
 
  // Get the minimum number of points in a Gaussian distribution, such that
  // the probability that the maximum of the distribution having the specified
  // zscore is 0.5. <src>zscore</src> should be non-negative.
  static inline uInt64 zscoreToNpts(Double zscore) {
    return (uInt64)(0.5 / erfc(zscore / sqrt(2)));
  }
 
 private:
  static std::map<uInt64, Double> _nptsToMaxZScore;
  static std::mutex _mutex;
};
 
}  // namespace casacore
 
#endif