Landau.h

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/* -*- mode: c++ -*- */

#ifndef _Landau_H_
#define _Landau_H_

#include "FunctionBase.h"

#include <cmath>

namespace hippodraw {

class MDL_HIPPOPLOT_API Landau : public FunctionBase
{
private:

  enum { peak, 
         norm, 
         sigma 
  };

protected:

  virtual void initialize ();

public:

  Landau ();

  Landau ( double peak, double counts, double sigma );

  virtual FunctionBase * clone () const;

  virtual double operator () ( double x ) const;

  virtual void initialParameters ( const FunctionHelper * helper );

  virtual bool hasDerivatives () const;

protected:

  //  virtual double derivByParm ( int i, double x ) const;

private:

  inline double calcY ( double x ) const 
  {
    return ( x - m_parms[peak] ) / m_parms[sigma];
  }

  inline double calcZ ( double x ) const
  {
    double y = calcY ( x );

        return -0.5 * ( 1.0 - std::exp ( -y ) );
  }

  double derivByNorm ( double x ) const;

  double derivByPeak ( double x ) const;

  double derivBySigma ( double x ) const;

};

} // namespace hippodraw

#endif // _Landau_H_