MnParabola.h

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// @(#)root/minuit2:$Id$
// Authors: M. Winkler, F. James, L. Moneta, A. Zsenei   2003-2005
 
/**********************************************************************
 *                                                                    *
 * Copyright (c) 2005 LCG ROOT Math team,  CERN/PH-SFT                *
 *                                                                    *
 **********************************************************************/
 
#ifndef ROOT_Minuit2_MnParabola
#define ROOT_Minuit2_MnParabola
 
#include <cmath>
 
namespace ROOT {
 
namespace Minuit2 {
 
/**
 
This class defines a parabola of the form a*x*x + b*x + c
 
@author Fred James and Matthias Winkler; comments added by Andras Zsenei
and Lorenzo Moneta
 
@ingroup Minuit
 
 */
 
class MnParabola {
 
public:
   /// Constructor that initializes the parabola with its three parameters.
   ///
   /// @param a the coefficient of the quadratic term.
   /// @param b the coefficient of the linear term.
   /// @param c the constant.
   MnParabola(double a, double b, double c) : fA(a), fB(b), fC(c) {}
 
   /// Evaluates the parabola a the point x.
   double Y(double x) const { return (fA * x * x + fB * x + fC); }
 
   /// Calculate the x coordinate of the Minimum of the parabola.
   double Min() const { return -fB / (2. * fA); }
 
   /// Calculate the y coordinate of the Minimum of the parabola.
   double YMin() const { return (-fB * fB / (4. * fA) + fC); }
 
   /// Get the coefficient of the quadratic term.
   double A() const { return fA; }
 
   /// Get the coefficient of the linear term.
   double B() const { return fB; }
 
   /// Get the coefficient of the constant term.
   double C() const { return fC; }
 
private:
   double fA;
   double fB;
   double fC;
};
 
} // namespace Minuit2
 
} // namespace ROOT
 
#endif // ROOT_Minuit2_MnParabola