RhoError.h

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#ifndef RHOERROR_H
#define RHOERROR_H
//                                                                      //
// RhoError                                                             //
//                                                                      //
// Error matrix class                                                   //
//                                                                      //
// Author: Marcel Kunze, RUB, Nov. 99                                   //
// Copyright (C) 1999-2001, Ruhr-University Bochum.                     //
// Ralf Kliemt, HIM/GSI Feb.2013 (Cleanup & Restructuring)              //
//                                                                      //

// Description:
//      A wrapper for a covariance matrix.  A covariance matrix is
//  a symmetric n X n matrix.  Change in chisq from point
//  covariance matrix was determined is just
//
//  diff * covariance^-1 * diff_transpose
//
//  which is implemented in a similarity transform in TMatrixD
//  the method determineChisq carries this calculation out and requires
//  the result to be a scalar.

#include <iostream>

#include <math.h>
#include "TVectorD.h"
#include "TMatrixD.h"
#include "TRotation.h"
#include "TLorentzRotation.h"

class RhoError : public TMatrixD {

 public:
  static const Double_t chisqUndef;

  RhoError(Int_t n, Double_t init = 0.0);

  // autocast copy constructor.  TMatrixD's promoted back
  // into TError matrices.

  RhoError(const TMatrixD &p);

  // new constructors for this class
  RhoError(const RhoError &v);

  RhoError &operator=(const RhoError &v);

  RhoError &operator=(const TMatrixD &v);

  // destructor MAY be needed later
  virtual ~RhoError(){};

  //----------------------------------------------------------------------
  // determineChisq
  //  Compute v^T * V^(-1)*v - ie the chisq for this covariance
  //  matrix and the difference vector v.
  //----------------------------------------------------------------------

  Double_t DetermineChisq(TVectorD &diff);

  // Get right signature for all operations performed on TError matrices
  // that should (and will) result in TError matrices.  These include
  // similarity transforms, transpose, inverse, matrix multiplication,
  // addition, and subtraction.  TMatrixD's as a result of operations
  // are promoted back into TError matrices if we start out
  // with TError matrices in the first place. (See copy constructors)

  RhoError &operator*=(Double_t t);

  //  TError& operator /= (Double_t t);

  //  TError& operator += (const TError& m2);

  //  TError& operator -= (const TError& m2);

  RhoError &operator-();

  // TError& Similarity(const TError& E);
  // implement E * covMatrix * E

  RhoError Similarity(const TMatrixD &m1) const;

  RhoError &SimilarityWith(const RhoError &m, const TMatrixD &m1);

  RhoError Similarity(const TRotation &rot) const;
  RhoError Similarity(const TLorentzRotation &rot) const;
  // When feasible implement R * covMatrix * R_transpose (= R^-1)

  Double_t Similarity(TVectorD &m1);
  TMatrixD SimilarityT(TMatrixD &m1);

 private:
  friend RhoError operator*(Double_t t, const RhoError &m1);

  friend RhoError operator*(const RhoError &m1, Double_t t);
  /*
  friend TError& operator/(Double_t t, const TError& m1);

  friend TError& operator/(const TError& m1, Double_t t);
  */
  friend RhoError operator+(const RhoError &m1, const RhoError &m2);

  friend RhoError operator-(const RhoError &m1, const RhoError &m2);

  friend std::ostream &operator<<(std::ostream &out, const RhoError &mat);
  friend std::istream &operator>>(std::istream &in, RhoError &mat);

 public:
  ClassDef(RhoError, 1) // Wrapper class for a covariance matrix
};

#endif