Two-fraction binned fit with RooFit not working

Hi! I’m relatively new to using ROOT so I apologize if my question is naive.

I’m attempting to fit two template histograms onto my data histogram with RooFit (I want to know how much of each template histogram RooFit thinks makes up my data histogram). I think I’ve almost got it, but I keep getting the error:

RooAddPdf::model[ mc1_yield * modelmc1 + mc2_yield * modelmc2 ]
getLogVal() top-level p.d.f evaluates to zero @ !refCoefNorm=(), !pdfs=(modelmc1 = 0/9969,modelmc2 = 0/9986), !coefficients=(mc1_yield = 0.1,mc2_yield = 0.1)

It seems like for some reason the fit doesn’t think that my first template (modelmc1) is not part of the data histogram at all. I can’t figure out why. Any help would be appreciated!! Here’s my code:

[code]// This is a re-do of the toy MC example, but *binned fit* with RooFit
// Uses two exponential functions ('templates' h1 and h2) of 1mil data points each, 
// from generate_out.root. Generates roofit_toymc.root and associated histograms
// C Bertsche Spring 2013

using namespace RooFit;


// S e t  u p  i n p u t  f i l e s
// --------------------------------

// Start with original MC templates, make scaled-down MCs and 'data'

	TFile *setA = TFile::Open("generate_out.root");
	TH1F *h1 = h1;					                // Get original MC templates (h1, h2)
	TH1F *h2 = h2;
	TH1F *h12 = new TH1F("h12","  ",500,0,10);	// Create 'data' (h12)
	TH1F *h1t = new TH1F("h1t","  ",500,0,10);  	// Create scaled MCs (h1t, h2t)
	TH1F *h2t = new TH1F("h2t","  ",500,0,10);

	for (int i=0;i<3000;i++)			// Fill 'data' (h12) with one MC template
   		Double_t life=h1->GetRandom();
  	for (int i=0;i<2000;i++)			// Fill 'data' (h12) with second MC template
   		Double_t life=h2->GetRandom();

	for (int i=0;i<10000;i++)			// Fill scaled MCs (h1t, h2t)
		Double_t life1=h1->GetRandom();
		Double_t life2=h2->GetRandom();
// Make RooFit histograms from input

	RooRealVar x("x","x",0.0,10.0);			

	RooDataHist data("data","data",x,h12);
	RooDataHist mc1("mc1","scaled mc1",x,h1t);
	RooDataHist mc2("mc2","scaled mc2",x,h2t);

	RooRealVar mc1_yield("mc1_yield","yield mc1",0.1,0,1);	 	// These are output variables
	RooRealVar mc2_yield("mc2_yield","yield of mc2",0.1,0,1); 	// These are output variables

// Make PDF from MC histograms
	RooHistPdf modelmc1("modelmc1","modelmc1",x, mc1);
	RooHistPdf modelmc2("modelmc2","modelmc2",x, mc2);

	RooAddPdf model("model", "model", RooArgList(modelmc1,modelmc2), RooArgList(mc1_yield,mc2_yield));	
									// Combines my MCs into one PDF model

// Plot the imported histogram(s)
	RooPlot* dframe = x.frame(Title("Data"));

	RooPlot* mc1frame = x.frame(Title("MC Scaled (1)"));

	RooPlot* mc2frame = x.frame(Title("MC Scaled (2)"));

	TCanvas* c = new TCanvas("roofit_example","RooFit FractionFit Example",800,1200);
	gROOT->SetStyle("Plain");	// Removes gray background from plots	
	c->cd(1) ; gPad->SetLeftMargin(0.15) ;   dframe->GetYaxis()->SetTitleOffset(1.4) ;   dframe->Draw();
	c->cd(2) ; gPad->SetLeftMargin(0.15) ; mc1frame->GetYaxis()->SetTitleOffset(1.4) ; mc1frame->Draw();
	c->cd(3) ; gPad->SetLeftMargin(0.15) ; mc2frame->GetYaxis()->SetTitleOffset(1.4) ; mc2frame->Draw();

// F i t  a n d  p l o t  m o d e l 
// -----------------------------------------------

// Now I have three RooDataHists: data, mc1, and mc2. They depend on RooRealVar x, x2, and x3 respectively
// The two MC RooDataHists have each been translated into a RooHistPdf ("modelmc1" and "modelmc2")
// The two RooHistPdf's have been combined into a RooAddPdf ("model")

	gROOT->SetStyle("Plain");	// removes gray background from plots

//	RooAbsReal* nll = model.createNLL(data,NumCPU(1)) ;	// From other example, looks like
//	RooAbsReal* pll_phi = nll->createProfile(mc1_yield) ;	// another way of doing the fitTo
//	RooMinuit(*nll).migrad();
//	RooMinuit(*nll).hesse();
//	RooMinuit(*nll).minos();  //optional

	model.fitTo(data);		// It is this fitTo command that gives the statistical output

	RooPlot* fitFrame=x.frame(Bins(50), Title("Fit Model"));
	data.plotOn(fitFrame, RooFit::LineColor(kRed));
	model.plotOn(fitFrame, LineStyle(kDashed));
	model.plotOn(fitFrame, Components("modelmc1"), LineColor(kGreen));
	model.plotOn(fitFrame, Components("modelmc2"), LineColor(kBlue));

	TCanvas* c6 = new TCanvas("c6","Fit Model",800,1200);
	gROOT->SetStyle("Plain");	// Removes gray background from plots	
	gPad->SetLeftMargin(0.15) ;   fitFrame->GetYaxis()->SetTitleOffset(1.4) ;   fitFrame->Draw();

	RooArgSet* params = model.getParameters(x);

// O u t p u t  r e s u l t s
// --------------------------