double getChisq(RooAbsData &dat, RooAbsPdf &pdf, RooRealVar &var, bool prt=false) {
// Find total number of events
double nEvt;
double nTot=0.0;
for(int j=0; j<dat.numEntries(); j++) {
dat.get(j);
nEvt=dat.weight();
nTot+=nEvt;
}
// Find chi-squared equivalent 2NLL
//RooRealVar *var=(RooRealVar*)(pdf.getParameters(*dat)->find("CMS_hgg_mass"));
double totNLL=0.0;
double prbSum=0.0;
for(int j=0; j<dat.numEntries(); j++) {
double m=dat.get(j)->getRealValue(var.GetName());
if ( m < var.getMin() || m > var.getMax()) continue;
// Find probability density and hence probability
var.setVal(m);
double prb = var.getBinWidth(0)*pdf.getVal(var);
prbSum+=prb;
dat.get(j);
nEvt=dat.weight();
double mubin=nTot*prb;
double contrib(0.);
if (nEvt < 1) contrib = mubin;
else contrib=mubin-nEvt+nEvt*log(nEvt/mubin);
totNLL+=contrib;
if(prt) cout << "Bin " << j << " prob = " << prb << " nEvt = " << nEvt << ", mu = " << mubin << " contribution " << contrib << endl;
}
totNLL*=2.0;
if(prt) cout << pdf.GetName() << " nTot = " << nTot << " 2NLL constant = " << totNLL << endl;
return totNLL;
}
