using namespace RooFit;

void linfit(){
  TFile *f = new TFile("Linefit.root");
  TTree *t = (TTree*)f->Get("G2 m4 T");
  
  RooRealVar En("Energy","Energy",690,790);

  RooRealVar mean("mean","mean",735);
  RooRealVar fwhm("fwhm","fwhm",5);
  RooGaussian gss("gss","gss",En,mean,fwhm);

  RooRealVar c1("c1","c1",1,-1000,1000);
  RooRealVar c2("c2","c2",1,-1000,1000);
  RooGenericPdf linear("linear","c1+c2*(Energy)",RooArgList(c1,c2,En));

  RooRealVar sigy("sigy","sigy",1,0,10000);
  RooRealVar bkgy("bkgy","bkgy",1,0,10000);

  RooAddPdf model("model","model",RooArgList(gss,linear),RooArgList(sigy,bkgy));

  RooDataSet data("data","data",RooArgSet(En),Import(*t));

  model.fitTo(data,Range(690,790),Extended());

  RooPlot *P = En.frame();
  data.plotOn(P);
  model.plotOn(P);
  model.plotOn(P,Components(gss),LineColor(kRed));
  P->Draw();
}