// This effectively does the same as the line above
RooAbsReal* nll = addpdf2a.createNLL(data,RooFit::Extended(kTRUE));
RooMinuit m(*nll) ;
m.migrad() ;
m.hesse() ;
// Now use the MINUIT session to make a contour plot
RooPlot* p1 = m.contour(var1,var2,1,2,3) ;
p1->Draw() ;