using namespace RooFit ;

void myfit()
{
  TFile *f = new TFile("fbetti_workspace.root") ;

  RooWorkspace* w = (RooWorkspace*) f->Get("w") ;

  RooRealVar* B0mES = w->var("B0mES");
  RooRealVar* B0DeltaE = w->var("B0DeltaE");
  RooRealVar* NSIG = w->var("NSIG");
  RooRealVar* mSIG_mES = w->var("m_{SIG}(m_{ES})");
  RooRealVar* sigmaSIG_mES = w->var("#sigma_{SIG}(m_{ES})");
  RooRealVar* aSIG_mES = w->var("a_{SIG}(m_{ES})");
  RooRealVar* nSIG_mES = w->var("n_{SIG}(m_{ES})");
  RooRealVar* m1SIG_DeltaE = w->var("m1_{SIG}(#DeltaE)");
  RooRealVar* m2SIG_DeltaE = w->var("m2_{SIG}(#DeltaE)");
  RooRealVar* sigma1SIG_DeltaE = w->var("#sigma1_{SIG}(#DeltaE)");
  RooRealVar* sigma2SIG_DeltaE = w->var("#sigma2_{SIG}(#DeltaE)");
  RooRealVar* fGau1SIG_DeltaE = w->var("f(Gau1)_{SIG}(#DeltaE)");
  RooAbsPdf* PsDataPDF = w->pdf("PsDataPDF") ;
  RooAbsData* dsPsData = w->data("dsPsData") ;

  // Now I fix all the parameters
  RooArgSet* param = PsDataPDF->getParameters(RooArgSet(*B0mES,*B0DeltaE));
  //param->Print();
  TIterator * iter = param->createIterator();
  RooRealVar * var;
  while(0 != (var= (RooRealVar*)iter->Next())) {
    // Fix this parameter:
    var->setConstant(kTRUE);
  }

  // I want the parameters of the signal to be floating in the ranges obtained by a previous fit on MonteCarlo
  NSIG->setConstant(kFALSE);
  mSIG_mES->setConstant(kFALSE);
  sigmaSIG_mES->setConstant(kFALSE);
  aSIG_mES->setRange(aSIG_mES->getVal()-aSIG_mES->getError(),aSIG_mES->getVal()+aSIG_mES->getError());
  aSIG_mES->setConstant(kFALSE);
  nSIG_mES->setRange(nSIG_mES->getVal()-nSIG_mES->getError(),nSIG_mES->getVal()+nSIG_mES->getError());
  nSIG_mES->setConstant(kFALSE);
  m1SIG_DeltaE->setRange(m1SIG_DeltaE->getVal()-m1SIG_DeltaE->getError(),m1SIG_DeltaE->getVal()+m1SIG_DeltaE->getError());
  m1SIG_DeltaE->setConstant(kFALSE);
  m2SIG_DeltaE->setRange(m2SIG_DeltaE->getVal()-m2SIG_DeltaE->getError(),m2SIG_DeltaE->getVal()+m2SIG_DeltaE->getError());
  m2SIG_DeltaE->setConstant(kFALSE);
  sigma1SIG_DeltaE->setRange(sigma1SIG_DeltaE->getVal()-sigma1SIG_DeltaE->getError(),sigma1SIG_DeltaE->getVal()+sigma1SIG_DeltaE->getError());
  sigma1SIG_DeltaE->setConstant(kFALSE);
  sigma2SIG_DeltaE->setRange(sigma2SIG_DeltaE->getVal()-sigma2SIG_DeltaE->getError(),sigma2SIG_DeltaE->getVal()+sigma2SIG_DeltaE->getError());
  sigma2SIG_DeltaE->setConstant(kFALSE);
  fGau1SIG_DeltaE->setRange(fGau1SIG_DeltaE->getVal()-fGau1SIG_DeltaE->getError(),fGau1SIG_DeltaE->getVal()+fGau1SIG_DeltaE->getError());
  fGau1SIG_DeltaE->setConstant(kFALSE);
  
  // ---------------
  // Fit pseudodata
  // ---------------
  RooFitResult* fitPsData = PsDataPDF->fitTo(*dsPsData,Save(),Extended(1),SumW2Error(kTRUE));
  fitPsData->Print();
  
}