void rootFit(){ TCanvas *c1 = new TCanvas("c1","",600,600); c1->Divide(1,2); TNtuple *T = new TNtuple("T","","x:y:z"); T->ReadFile("histogramData.dat"); T->Draw("y:x"); Double_t *X = T->GetV1(); Double_t *Y = T->GetV2(); for(int loop = 0; loop < 120; loop++){ cout << X[loop] << " " << Y[loop] << endl; } c1->Clear(); TGraph *graphT = new TGraph(120,Y,X); TGraph *graphB = new TGraph(120,Y,X); c1->cd(1); graphT->Draw("APL"); graphT->Fit("gaus+pol2","RME"); }