JRegressor.hh

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#ifndef __JFIT__JREGRESSOR__
#define __JFIT__JREGRESSOR__

#include "Jeep/JMessage.hh"


/**
 * \file
 * General purpose data regression method.
 * \author mdejong
 */
namespace JFIT {}
namespace JPP { using namespace JFIT; }

namespace JFIT {

  using JEEP::JMessage;
  
  
  /**
   * Abstract minimiser.
   * This "minimiser" can be used to determine the chi2 of the data for a given model value.
   */
  template<class JModel_t>
  struct JAbstractMinimiser :
    public JMessage< JAbstractMinimiser<JModel_t> >
  {
    typedef double                                      result_type;

    /**
     * Default constructor.
     */
    JAbstractMinimiser() 
    {}


    /**
     * Get chi2.
     *
     * \param  fit            fit function
     * \param  __begin        begin of data
     * \param  __end          end   of data
     * \return                chi2
     */
    template<class JFunction_t, class T>
    result_type operator()(const JFunction_t& fit, T __begin, T __end) 
    {
      double chi2 = 0.0;

      for (T i = __begin; i != __end; ++i) {
        chi2 += fit(value, *i);
      }

      return chi2;
    }

    JModel_t value;    //!< model value
  };


  /**
   * Template definition of a data regressor of given model.
   *
   * The first template argument refers to the model that should be fitted to the data and
   * the second to the type of minimiser.
   */
  template<class JModel_t, template<class> class JMinimiser_t = JAbstractMinimiser>
  struct JRegressor;


  /**
   * Abstract class for global fit method.
   */
  template<class JModel_t, template<class> class JMinimiser_t = JAbstractMinimiser>
  struct JAbstractRegressor :
    public JMinimiser_t<JModel_t>
  {
    typedef JMinimiser_t<JModel_t>                      minimiser_type;
    typedef JRegressor<JModel_t, JMinimiser_t>          regressor_type;
    typedef typename minimiser_type::result_type        result_type;


    /**
     * Global fit.
     *
     * \param  value              start value
     * \param  __begin            begin of data set
     * \param  __end              end   of data set
     * \return                    chi2
     */
    template<class T>
    result_type operator()(const JModel_t& value, T __begin, T __end)
    {
      static_cast<minimiser_type&>(*this).value = value;

      return static_cast<minimiser_type&>(*this)(static_cast<regressor_type&>(*this), __begin, __end);
    }
  };
}

#endif