fitslicesy.C

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/// \file
/// \ingroup tutorial_fit
/// \notebook -js
/// Illustrates how to use the TH1::FitSlicesY function
/// It uses the TH2F histogram generated in macro hsimple.C
/// It invokes FitSlicesY and draw the fitted "mean" and "sigma"
/// in 2 sepate pads.
/// This macro shows also how to annotate a picture, change
/// some pad parameters.
///
/// \macro_image
/// \macro_output
/// \macro_code
///
/// \author Rene Brun
 
#include <TCanvas.h>
#include <TFile.h>
#include <TH2F.h>
#include <TROOT.h>
#include <TStyle.h>
 
void fitslicesy() {
// Change some default parameters in the current style
   gStyle->SetLabelSize(0.06,"x");
   gStyle->SetLabelSize(0.06,"y");
   gStyle->SetFrameFillColor(38);
   gStyle->SetTitleW(0.6);
   gStyle->SetTitleH(0.1);
 
// Connect the input file and get the 2-d histogram in memory
   TString dir = gROOT->GetTutorialDir();
   dir.Append("/hsimple.C");
   dir.ReplaceAll("/./","/");
   if (!gInterpreter->IsLoaded(dir.Data())) gInterpreter->LoadMacro(dir.Data());
   TFile *hsimpleFile = (TFile*)gROOT->ProcessLineFast("hsimple(1)");
   if (!hsimpleFile) return;
   TH2F *hpxpy = (TH2F*)hsimpleFile->Get("hpxpy");
 
// Create a canvas and divide it
   TCanvas *c1 = new TCanvas("c1","c1",700,500);
   c1->SetFillColor(42);
   c1->Divide(2,1);
   TPad *leftPad = (TPad*)c1->cd(1);;
   leftPad->Divide(1,2);
 
// Draw 2-d original histogram
   leftPad->cd(1);
   gPad->SetTopMargin(0.12);
   gPad->SetFillColor(33);
   hpxpy->Draw();
   hpxpy->GetXaxis()->SetLabelSize(0.06);
   hpxpy->GetYaxis()->SetLabelSize(0.06);
   hpxpy->SetMarkerColor(kYellow);
 
// Fit slices projected along Y fron bins in X [7,32] with more than 20 bins  in Y filled
   hpxpy->FitSlicesY(nullptr,7,32,20);
 
// Show fitted "mean" for each slice
   leftPad->cd(2);
   gPad->SetFillColor(33);
   TH2F *hpxpy_0 = (TH2F*)hsimpleFile->Get("hpxpy_0");
   hpxpy_0->Draw();
   TPad *rightPad = (TPad*)c1->cd(2);
   rightPad->Divide(1,2);
   rightPad->cd(1);
   gPad->SetTopMargin(0.12);
   gPad->SetLeftMargin(0.15);
   gPad->SetFillColor(33);
   TH2F *hpxpy_1 = (TH2F*)hsimpleFile->Get("hpxpy_1");
   hpxpy_1->Draw();
 
// Show fitted "sigma" for each slice
   rightPad->cd(2);
   gPad->SetTopMargin(0.12);
   gPad->SetLeftMargin(0.15);
   gPad->SetFillColor(33);
   TH2F *hpxpy_2 = (TH2F*)hsimpleFile->Get("hpxpy_2");
   hpxpy_2->SetMinimum(0.8);
   hpxpy_2->Draw();
 
//attributes
   hpxpy_0->SetLineColor(5);
   hpxpy_1->SetLineColor(5);
   hpxpy_2->SetLineColor(5);
   hpxpy_0->SetMarkerColor(2);
   hpxpy_1->SetMarkerColor(2);
   hpxpy_2->SetMarkerColor(2);
   hpxpy_0->SetMarkerStyle(21);
   hpxpy_1->SetMarkerStyle(21);
   hpxpy_2->SetMarkerStyle(21);
   hpxpy_0->SetMarkerSize(0.6);
   hpxpy_1->SetMarkerSize(0.6);
   hpxpy_2->SetMarkerSize(0.6);
}