G4DataInterpolation.hh

Go to the documentation of this file.

//
// ********************************************************************
// * License and Disclaimer                                           *
// *                                                                  *
// * The  Geant4 software  is  copyright of the Copyright Holders  of *
// * the Geant4 Collaboration.  It is provided  under  the terms  and *
// * conditions of the Geant4 Software License,  included in the file *
// * LICENSE and available at  http://cern.ch/geant4/license .  These *
// * include a list of copyright holders.                             *
// *                                                                  *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work  make  any representation or  warranty, express or implied, *
// * regarding  this  software system or assume any liability for its *
// * use.  Please see the license in the file  LICENSE  and URL above *
// * for the full disclaimer and the limitation of liability.         *
// *                                                                  *
// * This  code  implementation is the result of  the  scientific and *
// * technical work of the GEANT4 collaboration.                      *
// * By using,  copying,  modifying or  distributing the software (or *
// * any work based  on the software)  you  agree  to acknowledge its *
// * use  in  resulting  scientific  publications,  and indicate your *
// * acceptance of all terms of the Geant4 Software license.          *
// ********************************************************************
//
// G4DataInterpolation
//
// Class description:
//
// The class consists of some methods for data interpolations and
// extrapolations. The methods based mainly on recommendations given in the
// book: An introduction to NUMERICAL METHODS IN C++, B.H. Flowers,
//       Claredon Press, Oxford, 1995.
 
// Author: V.Grichine, 03.04.1997
// --------------------------------------------------------------------
#ifndef G4DATAINTERPOLATION_HH
#define G4DATAINTERPOLATION_HH 1
 
#include "globals.hh"
 
class G4DataInterpolation
{
 public:
  G4DataInterpolation(G4double pX[], G4double pY[], G4int number);
  // Constructor for initializing data members.
 
  G4DataInterpolation(G4double pX[], G4double pY[], G4int number,
                      G4double pFirstDerStart, G4double pFirstDerFinish);
  // Constructor for cubic spline interpolation. It creates fSecond Deivative
  // array as well as fArgument and fFunction.
 
  ~G4DataInterpolation();
  // Destructor deletes dynamically created arrays for data members: fArgument,
  // fFunction and fSecondDerivative, all have dimension of fNumber.
 
  G4DataInterpolation(const G4DataInterpolation&) = delete;
  G4DataInterpolation& operator=(const G4DataInterpolation&) = delete;
  // Copy constructor and assignement operator not allowed.
 
  G4double PolynomInterpolation(G4double pX, G4double& deltaY) const;
  // This function returns the value P(pX), where P(x) is polynom of fNumber-1
  // degree such that P(fArgument[i]) = fFunction[i], for i = 0, ..., fNumber-1.
 
  void PolIntCoefficient(G4double cof[]) const;
  // Given arrays fArgument[0,..,fNumber-1] and fFunction[0,..,fNumber-1], this
  // function calculates an array of coefficients.
  // The coefficients don't provide usually (fNumber>10) better accuracy for
  // polynom interpolation, as compared with PolynomInterpolation() function.
  // They could be used instead for derivate calculations and some other
  // applications.
 
  G4double RationalPolInterpolation(G4double pX, G4double& deltaY) const;
  // The function returns diagonal rational function (Bulirsch and Stoer
  // algorithm of Neville type) Pn(x)/Qm(x) where P and Q are polynoms.
  // Tests showed the method is not stable and hasn't advantage if compared
  // with polynomial interpolation.
 
  G4double CubicSplineInterpolation(G4double pX) const;
  // Cubic spline interpolation in point pX for function given by the table:
  // fArgument, fFunction. The constructor, which creates fSecondDerivative,
  // must be called before. The function works optimal, if sequential calls
  // are in random values of pX.
 
  G4double FastCubicSpline(G4double pX, G4int index) const;
  // Return cubic spline interpolation in the point pX which is located between
  // fArgument[index] and fArgument[index+1]. It is usually called in sequence
  // of known from external analysis values of index.
 
  G4int LocateArgument(G4double pX) const;
  // Given argument pX, returns index k, so that pX bracketed by fArgument[k]
  // and fArgument[k+1].
 
  void CorrelatedSearch(G4double pX, G4int& index) const;
  // Given a value pX, returns a value 'index' such that pX is between
  // fArgument[index] and fArgument[index+1]. fArgument MUST BE MONOTONIC,
  // either increasing or decreasing. If index = -1 or fNumber, this indicates
  // that pX is out of range. The value index on input is taken as the initial
  // approximation for index on output.
 
 private:
  // pointers to data table to be interpolated for y[i] and x[i] respectively
  G4double* fArgument = nullptr;
  G4double* fFunction = nullptr;
 
  G4double* fSecondDerivative = nullptr;
 
  G4int fNumber = 0;  // the corresponding table size
};
 
#endif