Gabriele Cosmo
63 lines
1.8 KiB
C++
63 lines
1.8 KiB
C++
//
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// Fit of longitudinal profile with Gamma function
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// See Review of Particles Physics - Electromagnetic cascades
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//
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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Double_t GammaFunction(Double_t* t, Double_t* params ) {
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if (ROOT::TMath::Gamma(params[0]) != 0 ) {
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return (100 * pow(params[1],params[0]) / ROOT::TMath::Gamma(params[0]))
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* pow(t[0],(params[0]-1)) * exp (-params[1]*t[0]);
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} else {
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return 0;
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}
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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void GammaFit() {
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cout
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<< "Try fit [100*pow(b,a)/ROOT::TMath::Gamma(a)] * pow(t,(a-1)) * exp(-b*t)"
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<< endl;
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TFile* f = new TFile("93ref0.root");
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TH1D* h1 = (TH1D*) f->Get("4");
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//put error in h1
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TH1D* h2 = (TH1D*) f->Get("5");
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int nmax = h1->GetNbinsX();
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for (int n=0; n<nmax; n++) {
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Double_t er = h2->GetBinContent(n);
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h1->SetBinError(n,er);
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}
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TF1* func = new TF1("fit", GammaFunction,-0.5,40.,2);
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func->SetParameter(0,1.);
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func->SetParameter(1,1.);
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func->SetParNames("a", "b");
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h1->Fit("fit","r","");
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h1->SetMarkerColor(kRed);
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h1->SetMarkerStyle(3);
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h1->Draw("epl");
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Double_t a = func->GetParameter(0);
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Double_t b = func->GetParameter(1);
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Double_t tmax = (a-1)/b;
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// Chi-square distribution
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double chisq=func->GetChisquare();
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double ndf=func->GetNDF();
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double chisqdf=chisq/ndf;
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gStyle->SetOptFit(1111);
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cout << "----------------------------------------------";
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cout << "\n Chisquare: " << chisq << " / " << ndf << " = " << chisqdf;
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cout << "\n----------------------------------------------";
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cout << "\n a = " << a;
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cout << "\n b = " << b;
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cout << "\n tmax = " << tmax;
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cout << "\n----------------------------------------------" << endl;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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