Please do not get confused by the name of the file. The code performs a time...

Please do not get confused by the name of the file. The code performs a time walk fit to the data for one pixel

caliberation.C

+void caliberation (){
+  auto c=new TCanvas();
+  gStyle->SetOptFit(1);
+
+  TGraphErrors* graph = new TGraphErrors("125_125.txt","%lg %lg %lg","");
+  graph->SetTitle(" ");
+  graph->GetXaxis()->SetTitle("Voltage [mV]");
+  graph->GetYaxis()->SetTitle("Time difference [ns]");
+  graph->SetMarkerStyle(8);
+  graph->SetMarkerColor(4);
+  // graph->GetYaxis()->SetRangeUser(15.5,17.35);
+  
+
+  TF1 *fitfuncTOA = new TF1("fitfuncTOA","(([0]/(x-[1]))+ [2])",25.0,700.0);
+  fitfuncTOA->SetParNames("curvature","asymtote","offset");
+ 
+    
+  fitfuncTOA->SetParameter(0,600.0);
+
+  auto ymax = TMath::MaxElement(graph->GetN(),graph->GetY());
+  auto ttoa = graph->Eval(ymax);
+  //  cout << ymax << " " << ttoa;
+  fitfuncTOA->SetParameter(1,ttoa);
+
+  auto dtoa = graph->Eval(688.35);
+  fitfuncTOA->SetParameter(2,dtoa);
+  fitfuncTOA->SetLineColor(kRed);
+  graph->Fit(fitfuncTOA,"R");
+  graph->Draw("AP");
+
+}