RooPolyVar.cxx

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/*****************************************************************************
 * Project: RooFit                                                           *
 * Package: RooFitCore                                                       *
 * @(#)root/roofitcore:$Id: RooPolyVar.cxx 26044 2008-10-31 16:45:22Z wouter $
 * Authors:                                                                  *
 *   WV, Wouter Verkerke, UC Santa Barbara, verkerke@slac.stanford.edu       *
 *   DK, David Kirkby,    UC Irvine,         dkirkby@uci.edu                 *
 *                                                                           *
 * Copyright (c) 2000-2005, Regents of the University of California          *
 *                          and Stanford University. All rights reserved.    *
 *                                                                           *
 * Redistribution and use in source and binary forms,                        *
 * with or without modification, are permitted according to the terms        *
 * listed in LICENSE (http://roofit.sourceforge.net/license.txt)             *
 *****************************************************************************/

//////////////////////////////////////////////////////////////////////////////
//
// BEGIN_HTML
// Class RooPolyVar is a RooAbsReal implementing a polynomial in terms
// of a list of RooAbsReal coefficients
// <pre>
// f(x) = sum_i a_i * x
// </pre>
// Class RooPolyvar implements analytical integrals of all polynomials
// it can define.
// END_HTML
//

#include "RooFit.h"

#include "Riostream.h"
#include "Riostream.h"
#include <math.h>
#include "TMath.h"

#include "RooPolyVar.h"
#include "RooAbsReal.h"
#include "RooRealVar.h"
#include "RooArgList.h"
#include "RooMsgService.h"
#include "TMath.h"

ClassImp(RooPolyVar)
;


//_____________________________________________________________________________
RooPolyVar::RooPolyVar()
{
  // Default constructor
  _coefIter = _coefList.createIterator() ;
}


//_____________________________________________________________________________
RooPolyVar::RooPolyVar(const char* name, const char* title, 
                             RooAbsReal& x, const RooArgList& coefList, Int_t lowestOrder) :
  RooAbsReal(name, title),
  _x("x", "Dependent", this, x),
  _coefList("coefList","List of coefficients",this),
  _lowestOrder(lowestOrder) 
{
  // Construct polynomial in x with coefficients in coefList. If
  // lowestOrder is not zero, then the first element in coefList is
  // interpreted as as the 'lowestOrder' coefficients and all
  // subsequent coeffient elements are shifted by a similar amount.


  _coefIter = _coefList.createIterator() ;

  // Check lowest order
  if (_lowestOrder<0) {
    coutE(InputArguments) << "RooPolyVar::ctor(" << GetName() 
                          << ") WARNING: lowestOrder must be >=0, setting value to 0" << endl ;
    _lowestOrder=0 ;
  }

  TIterator* coefIter = coefList.createIterator() ;
  RooAbsArg* coef ;
  while((coef = (RooAbsArg*)coefIter->Next())) {
    if (!dynamic_cast<RooAbsReal*>(coef)) {
      coutE(InputArguments) << "RooPolyVar::ctor(" << GetName() << ") ERROR: coefficient " << coef->GetName() 
                            << " is not of type RooAbsReal" << endl ;
      assert(0) ;
    }
    _coefList.add(*coef) ;
  }
  delete coefIter ;
}



//_____________________________________________________________________________
RooPolyVar::RooPolyVar(const char* name, const char* title,
                           RooAbsReal& x) :
  RooAbsReal(name, title),
  _x("x", "Dependent", this, x),
  _coefList("coefList","List of coefficients",this),
  _lowestOrder(1)
{
  // Constructor of flat polynomial function

  _coefIter = _coefList.createIterator() ;
}                                                                                                                                 



//_____________________________________________________________________________
RooPolyVar::RooPolyVar(const RooPolyVar& other, const char* name) :
  RooAbsReal(other, name), 
  _x("x", this, other._x), 
  _coefList("coefList",this,other._coefList),
  _lowestOrder(other._lowestOrder) 
{
  // Copy constructor
  _coefIter = _coefList.createIterator() ;
}




//_____________________________________________________________________________
RooPolyVar::~RooPolyVar() 
{
  // Destructor
  delete _coefIter ;
}




//_____________________________________________________________________________
Double_t RooPolyVar::evaluate() const 
{
  // Calculate and return value of polynomial

  Double_t sum(0) ;
  Int_t order(_lowestOrder) ;
  _coefIter->Reset() ;

  RooAbsReal* coef ;
  const RooArgSet* nset = _coefList.nset() ;
  while((coef=(RooAbsReal*)_coefIter->Next())) {
    sum += coef->getVal(nset)*TMath::Power(_x,order++) ;
  }

  return sum;
}



//_____________________________________________________________________________
Int_t RooPolyVar::getAnalyticalIntegral(RooArgSet& allVars, RooArgSet& analVars, const char* /*rangeName*/) const 
{
  // Advertise that we can internally integrate over x

  if (matchArgs(allVars, analVars, _x)) return 1;
  return 0;
}



//_____________________________________________________________________________
Double_t RooPolyVar::analyticalIntegral(Int_t code, const char* rangeName) const 
{
  // Calculate and return analytical integral over x

  assert(code==1) ;

  Double_t sum(0) ;

  const RooArgSet* nset = _coefList.nset() ;
  Int_t order(_lowestOrder) ;
  _coefIter->Reset() ;
  RooAbsReal* coef ;

  // Primitive = sum(k) coef_k * 1/(k+1) x^(k+1)
  while((coef=(RooAbsReal*)_coefIter->Next())) {
    sum += coef->getVal(nset)*(TMath::Power(_x.max(rangeName),order+1)-TMath::Power(_x.min(rangeName),order+1))/(order+1) ; 
    order++ ;
  }

  return sum;  
  
}

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