using namespace RooFit;
void frac()
 {
    TCanvas* c1 = new TCanvas("c", "", 550, 450);

    TF1 f("f", "gaus(0)+pol2(3)", 0, 10);
    TF1 f1("f1", "gaus", 0, 10);
    TF1 f2("f2", "pol2", 0, 10);
    f.SetParameter(0, 100);
    f.SetParameter(1, 5);
    f.SetParameter(2, 1);
    f.SetParameter(3, 10);
    f.SetParameter(4, 1);
    f.SetParameter(5, 0.5);

    f1.SetParameter(0, 100);
    f1.SetParameter(1, 5);
    f1.SetParameter(2, 1);

    f2.SetParameter(0, 10);
    f2.SetParameter(1, 1);
    f2.SetParameter(2, 0.5);

    TH1D* h = new TH1D("h", "", 100, 0, 10);
    h->FillRandom("f");
    h->Draw();
    TH1D* h1 = new TH1D("h1", "", 100, 0, 10);
    h1->FillRandom("f1");
    TH1D* h2 = new TH1D("h2", "", 100, 0, 10);
    h2->FillRandom("f2");

    h1->Sumw2();
    h2->Sumw2();
    h->Sumw2();

    h1->Scale(1./h1->Integral());
    h2->Scale(1./h2->Integral());
    h->Scale(1./h->Integral());


    RooRealVar x("x", "x", 0, 10);
    RooRealVar frac1("frac1", "frac1", 0.5);
    RooDataHist hist1("hist1", "hist1", RooArgList(x), h1);
    RooDataHist hist2("hist2", "hist2", RooArgList(x), h2);
	    RooDataHist hsum("hsum", "hsum", RooArgList(x), h);
    RooHistPdf f_1("f_1", "f_1", RooArgList(x), hist1, 0);
    RooHistPdf f_2("f_2", "f_2", RooArgList(x), hist2, 0);
    RooAddPdf sum("sum", "frac1+frac2", RooArgList(f_1, f_2), RooArgList(frac1), kTRUE);

    sum.fitTo(hsum, SumW2Error(kTRUE));
}