Example13.cxx

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// $Id$
//-----------------------------------------------------------------------
//       The GSI Online Offline Object Oriented (Go4) Project
//         Experiment Data Processing at EE department, GSI
//-----------------------------------------------------------------------
// Copyright (C) 2000- GSI Helmholtzzentrum fuer Schwerionenforschung GmbH
//                     Planckstr. 1, 64291 Darmstadt, Germany
// Contact:            http://go4.gsi.de
//-----------------------------------------------------------------------
// This software can be used under the license agreements as stated
// in Go4License.txt file which is part of the distribution.
//-----------------------------------------------------------------------

// Go4Fit Example N13

#ifndef __CINT__

#include <iostream>

#include "TMath.h"
#include "TH1.h"
#include "TH2.h"
#include "TCanvas.h"
#include "TCutG.h"
#include "TApplication.h"
#include "TRandom.h"

#include "TGo4Fitter.h"
#include "TGo4FitDataHistogram.h"
#include "TGo4FitDataRidge.h"
#include "TGo4FitModelFormula.h"

void Example13();

int main(int argc, char **argv)
{
   TApplication theApp("Application", nullptr, nullptr);

   Example13();

   theApp.Run();

   return 0;
}

#endif

void AddRidge(TH2D *histo, double a, double k, double b, double xstart, int numsteps, int numpoints, double deviation)
{
   TRandom rnd(1234);

   double x = xstart;

   for (int i = 0; i < numsteps; i++) {
      double y = a * exp(k * x) + b;

      double alf = TMath::ATan(k * a * exp(k * x)) + TMath::Pi() / 2.;

      for (int j = 0; j < numpoints; j++) {
         double radius = rnd.Gaus(0., deviation);
         histo->Fill(x + radius * cos(alf), y + radius * sin(alf));
      }

      x = x + 0.001 * sin(alf);
   }
}

TH2D *MakeRidgeHistogram()
{
   TH2D *histo = new TH2D("Histo", "Ridge y = a*exp(k*x)+b", 100, 0., 10., 100, 0., 10.);

   std::cout << "Generating histogram " << std::endl;

   AddRidge(histo, 10, -0.3, 2, 1.5, 10000, 100, 0.3);

   AddRidge(histo, 10, -0.5, 0, 0.5, 10000, 50, 0.2);

   AddRidge(histo, 10, -0.1, +2, 3.5, 10000, 50, 0.2);

   std::cout << "   Done " << std::endl;

   return histo;
}

TCutG *MakeCut()
{
   Float_t xx[7] = {1.0, 4.0, 9.0, 9.5, 5.0, 2.0, 1.0};
   Float_t yy[7] = {8.0, 2.5, 2.0, 4.0, 6.0, 9.5, 8.0};
   return new TCutG("RangeCut", 7, xx, yy);
}

void Example13()
{
   // model histogram with ridge with exponential function
   TH2D *histo = MakeRidgeHistogram();
   new TCanvas("Canvas1");
   histo->Draw("LEGO2");

   // create fitter, select fit function and not add standard actions list
   TGo4Fitter fitter("Fitter", TGo4Fitter::ff_chi_square, kFALSE);

   // create data object to represent of two-dimensional histogram
   // bins, which are less then 3 are excluded
   // select middle ridge by TCutG object
   TGo4FitDataHistogram *datah = new TGo4FitDataHistogram("histogram", histo);
   datah->SetExcludeLessThen(3);
   datah->AddRangeCut(MakeCut());

   // create ridge object, which select axis number 1 (y axis) as function of the rest coordinates
   TGo4FitDataRidge *ridge = new TGo4FitDataRidge("ridge", datah, 1);
   fitter.AddData(ridge);

   // create formula function to approximate ridge function
   // specific range and initial values for parameters need to be set
   TGo4FitModelFormula *model = new TGo4FitModelFormula("RidgeFunc", "parA*exp(parK*x)+parB", 3, kFALSE);
   model->SetRange(0, 2, 8.);
   model->SetParsNames("parA", "parK", "parB");
   model->SetParsValues(9., -0.2, 1.2);
   fitter.AddModel("ridge", model);

   // add minuit action
   fitter.AddSimpleMinuit();

   // use memory buffers for data objects
   fitter.SetMemoryUsage(1);

   // execute actions
   fitter.DoActions();

   // print parameters values
   fitter.Print("Pars");

   // draw results of fit
   fitter.Draw("#ridge");
}