Dear experts - I have a quick (and hopefully very simple question) 
I have 3 RooDatasets which contain the same variables, but different numbers of entries. I wish to see if the dataset distributions (for a given variable) are ~the same and hence I want to scale the plots of the more sparse datasets to have the same number of entries/area as the most populated data set. I tried to use the code below and the plotOn(Rescale(scale)) optionā¦but running the code with and without the Rescale option I get the same result - could anyone explain this given the relevant (havenāt put in all the gory codingā¦) code lines below? Any help is very much appreciated 
Thanks and merry Xmas Sam
// Create some RooDataSets from the old ones....
RooDataSet * Data_new = new RooDataSet("Data_new","Data_new", (observables,*Mother_mass_var)); Data_new = (RooDataSet*)Data.reduce("sqrt(Mother_mass_squared)>1700");
RooDataSet * Data_new2 = new RooDataSet("Data_new2","Data_new2", (observables,*Mother_mass_var));
Data_new2 = (RooDataSet*)Data2.reduce("sqrt(Mother_mass_squared)>1700");
RooDataSet * Data_new3 = new RooDataSet("Data_new3","Data_new3", (observables,*Mother_mass_var)); Data_new3 = (RooDataSet*)Data3.reduce("sqrt(Mother_mass_squared)>1700");
// Get the number of entries in the RooDataSets
Int_t num_entries_new = Data_new->numEntries();
Int_t num_entries_new2 = Data_new2->numEntries();
Int_t num_entries_new3 = Data_new3->numEntries();
// Calculate the scale factors for the RooDataSets
Double_t ScaleFactor = num_entries_new/num_entries_new2;
Double_t ScaleFactor2 = num_entries_new/num_entries_new3;
// Set up canvas TCanvas* c = new TCanvas("PIDK change","PID change",800,400) ;
// Draw the frames
RooPlot* xframe = Mother_mass_var->frame(Bins(100));
Data_new->plotOn(xframe,MarkerColor(kBlue));
Data_new->statOn(xframe);
RooPlot* yframe = Mother_mass_var2->frame(Bins(100)); Data_new2->plotOn(yframe,MarkerColor(kRed),Rescale(ScaleFactor));
Data_new2->statOn(yframe);
RooPlot* zframe = Mother_mass_var3->frame(Bins(100));
Data_new3->plotOn(zframe,MarkerColor(kOrange),Rescale(Scale_factor2));
Data_new3->statOn(zframe);
// Drawing setup
xframe->Draw();
yframe->Draw("SAME");
zframe->Draw("SAME") ;
c->Draw();