double StandardFrequentistDiscovery(
const char* infile = "",
const char* workspaceName = "channel1",
const char* modelConfigNameSB = "ModelConfig",
const char* dataName = "obsData",
int toys = 1000,
double poiValueForBackground = 0.0,
double poiValueForSignal = 1.0
) {
// The workspace contains the model for s+b. The b model is "autogenerated"
// by copying s+b and setting the one parameter of interest to zero.
// To keep the script simple, multiple parameters of interest or different
// functional forms of the b model are not supported.
// for now, assume there is only one parameter of interest, and these are
// its values:
/////////////////////////////////////////////////////////////
// First part is just to access a user-defined file
// or create the standard example file if it doesn't exist
////////////////////////////////////////////////////////////
const char* filename = "";
if (!strcmp(infile,"")) {
filename = "results/example_channel1_GammaExample_model.root";
bool fileExist = !gSystem->AccessPathName(filename); // note opposite return code
// if file does not exists generate with histfactory
if (!fileExist) {
#ifdef _WIN32
cout << "HistFactory file cannot be generated on Windows - exit" << endl;
return -1;
#endif
// Normally this would be run on the command line
cout <<"will run standard hist2workspace example"<<endl;
gROOT->ProcessLine(".! prepareHistFactory .");
gROOT->ProcessLine(".! hist2workspace config/example.xml");
cout <<"\n\n---------------------"<<endl;
cout <<"Done creating example input"<<endl;
cout <<"---------------------\n\n"<<endl;
}
}
else
filename = infile;
// Try to open the file
TFile *file = TFile::Open(filename);
// if input file was specified byt not found, quit
if(!file ){
cout <<"StandardRooStatsDemoMacro: Input file " << filename << " is not found" << endl;
return -1;
}
/////////////////////////////////////////////////////////////
// Tutorial starts here
////////////////////////////////////////////////////////////
TStopwatch *mn_t = new TStopwatch;
mn_t->Start();
// get the workspace out of the file
RooWorkspace* w = (RooWorkspace*) file->Get(workspaceName);
if (!w) {
cout << "workspace not found" << endl;
return -1.0;
}
// get the modelConfig out of the file
ModelConfig* mc = (ModelConfig*) w->obj(modelConfigNameSB);
// get the data out of the file
RooAbsData* data = w->data(dataName);
// make sure ingredients are found
if (!data || !mc) {
w->Print();
cout << "data or ModelConfig was not found" << endl;
return -1.0;
}
RooRealVar* firstPOI = (RooRealVar*) mc->GetParametersOfInterest()->first();
firstPOI->setVal(poiValueForSignal);
mc->SetSnapshot(*mc->GetParametersOfInterest());
// create null model
ModelConfig *mcNull = mc->Clone("ModelConfigNull");
firstPOI->setVal(poiValueForBackground);
mcNull->SetSnapshot(*(RooArgSet*)mcNull->GetParametersOfInterest()->snapshot());
// ----------------------------------------------------
// Configure a ProfileLikelihoodTestStat and a SimpleLikelihoodRatioTestStat
// to use simultaneously with ToyMCSampler
ProfileLikelihoodTestStat* plts = new ProfileLikelihoodTestStat(*mc->GetPdf());
plts->SetOneSidedDiscovery(true);
plts->SetVarName( "q_{0}/2" );
// ----------------------------------------------------
// configure the ToyMCImportanceSampler with two test statistics
ToyMCSampler toymcs(*plts, 50);
// Since this tool needs to throw toy MC the PDF needs to be
// extended or the tool needs to know how many entries in a dataset
// per pseudo experiment.
// In the 'number counting form' where the entries in the dataset
// are counts, and not values of discriminating variables, the
// datasets typically only have one entry and the PDF is not
// extended.
if (!mc->GetPdf()->canBeExtended()) {
if (data->numEntries() == 1) {
toymcs.SetNEventsPerToy(1);
} else cout << "Not sure what to do about this model" << endl;
}
// We can use PROOF to speed things along in parallel
// ProofConfig pc(*w, 2, "user@yourfavoriteproofcluster", false);
ProofConfig pc(*w, 2, "", false);
//toymcs.SetProofConfig(&pc); // enable proof
// instantiate the calculator
FrequentistCalculator freqCalc(*data, *mc, *mcNull, &toymcs);
freqCalc.SetToys( toys,toys ); // null toys, alt toys
// Run the calculator and print result
HypoTestResult* freqCalcResult = freqCalc.GetHypoTest();
freqCalcResult->GetNullDistribution()->SetTitle( "b only" );
freqCalcResult->GetAltDistribution()->SetTitle( "s+b" );
freqCalcResult->Print();
double pvalue = freqCalcResult->NullPValue();
// stop timing
mn_t->Stop();
cout << "total CPU time: " << mn_t->CpuTime() << endl;
cout << "total real time: " << mn_t->RealTime() << endl;
// plot
TCanvas* c1 = new TCanvas();
HypoTestPlot *plot = new HypoTestPlot(*freqCalcResult, 100, -0.49, 9.51 );
plot->SetLogYaxis(true);
// add chi2 to plot
int nPOI = 1;
TF1* f = new TF1("f", TString::Format("1*ROOT::Math::chisquared_pdf(2*x,%d,0)",nPOI), 0,20);
f->SetLineColor( kBlack );
f->SetLineStyle( 7 );
plot->AddTF1( f, TString::Format("#chi^{2}(2x,%d)",nPOI) );
plot->Draw();
c1->SaveAs("standard_discovery_output.pdf");
return pvalue;
}
