dEdxVsEang.cxx

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//This code is to fit graph gain vs eangle and get the slope
TString old_file = "../../Eangle1DSec/eangle.root";
TString new_file = "eangle.root";
 
void dEdxVsEang()
{
    TFile *f=new TFile(old_file);
    ostringstream strout;
    strout<<"ddgcalib";
    TTree *tree = (TTree*)f->Get(strout.str().c_str()); 
    double dedx[100],eangle[100], err[100];
    tree->SetBranchAddress("gain",dedx);
    tree->SetBranchAddress("eangle",eangle);
    tree->SetBranchAddress("fitmeanerr", err); 
    tree->GetEntry(0);
    double sum=0;
    for(int i=0;i<100;i++)
    {
        sum+=dedx[i];
    err[i] = err[i]/550;
    }
    sum = sum/100;
    gStyle->SetOptFit(0111);
    TCanvas *c1 = new TCanvas("c1","c1",10,10,800,642);
    //    TGraphErrors* gr = new TGraphErrors(100,eangle,dedx,eangle,err); 
    TGraph* gr = new TGraphErrors(100,eangle,dedx); 
    gr->SetMarkerColor(2);
    gr->SetLineColor(2);
    gr->Draw("A*");
 
    // graph of check
    f=new TFile(new_file);
    tree = (TTree*)f->Get(strout.str().c_str()); 
    double dedx2[100],eangle2[100], err2[100];
    tree->SetBranchAddress("gain",dedx2);
    tree->SetBranchAddress("eangle",eangle2);
    tree->SetBranchAddress("fitmeanerr", err2); 
    tree->GetEntry(0);
    double sum=0;
    for(int i=0;i<100;i++)
    {
        sum+=dedx[i];
    err[i] = err[i]/550;
    }
    sum = sum/100;
    TGraph* gr2 = new TGraphErrors(100,eangle2,dedx2); 
    gr2->Draw("*,same");
 
    TLegend* leg = new TLegend(.65, .75, .89, .89);
    leg->AddEntry(gr,"ori","p");
    leg->AddEntry(gr2,"cor","p");
    leg->Draw();
 
    TFile f_save("dEdxVsEang.root","recreate");
    c1->Write();
    f_save.Close();
    f->Close();
}