Time difference vs voltage is plotted

Time walk correction/TreeTest.C

@@ -83,6 +83,14 @@ void TreeTPWrite(){
   //Save only the new version of the tree 
 
   TPtree->Write("",TObject::kOverwrite);
+  
+  long N = TPtree->Draw("voltage:toa:sqrt(toa_var) ", "row==1 && col==10 && toa>0", "goff");
+  TGraphErrors *gr = new TGraphErrors(N,TPtree->GetV1(),TPtree->GetV2(),0,TPtree->GetV3());
+  gr->GetXaxis()->SetTitle("Volatge[mV]");
+  gr->GetYaxis()->SetTitle ("time difference[ns]");
+  gr->SetTitle(" ");
+  gr->SetMarkerStyle(7);
+  gr->Draw("AP");
   TPfile->Close();
 }