// --------------------------------------------------------------------------
//                   OpenMS -- Open-Source Mass Spectrometry
// --------------------------------------------------------------------------
// Copyright The OpenMS Team -- Eberhard Karls University Tuebingen,
// ETH Zurich, and Freie Universitaet Berlin 2002-2023.
//
// This software is released under a three-clause BSD license:
//  * Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//  * Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//  * Neither the name of any author or any participating institution
//    may be used to endorse or promote products derived from this software
//    without specific prior written permission.
// For a full list of authors, refer to the file AUTHORS.
// --------------------------------------------------------------------------
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL ANY OF THE AUTHORS OR THE CONTRIBUTING
// INSTITUTIONS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
// OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
// OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
// ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// --------------------------------------------------------------------------
// $Maintainer: Lars Nilse $
// $Authors: Lars Nilse $
// --------------------------------------------------------------------------

#pragma once

#include <OpenMS/CONCEPT/Exception.h>

#include <cmath>
#include <vector>

namespace OpenMS
{
  namespace Math
  {
    /**
      @brief This class offers functions to perform least-squares fits to a straight line model, \f$ Y(c,x) = c_0 + c_1 x \f$.

      @ingroup Math
    */
    class OPENMS_DLLAPI LinearRegressionWithoutIntercept
    {
      public:

      /// Constructor
      LinearRegressionWithoutIntercept();
      
      /**
       * @brief adds an observation (x,y) to the regression data set.
       *
       * @param x    independent variable value
       * @param y    dependent variable value
       */
      void addData(double x, double y);
      
      /**
       * @brief adds observations (x,y) to the regression data set.
       *
       * @param x    vector of independent variable values
       * @param y    vector of dependent variable values
       */
      void addData(std::vector<double>& x, std::vector<double>& y);
      
      /**
       * @brief returns the slope of the estimated regression line.
       */
      double getSlope() const;

      private:
      /**
       * @brief total variation in x
       */
      double sum_xx_;
      
      /**
       * @brief sum of products
       */
      double sum_xy_;
      
      /**
       * @brief number of observations
       */
      int n_;
      
    };

  } // namespace Math
} // namespace OpenMS


