rs701_BayesianCalculator¶

%%cpp -d
#include "RooRealVar.h"
#include "RooWorkspace.h"
#include "RooDataSet.h"
#include "RooPlot.h"
#include "RooMsgService.h"

#include "RooStats/BayesianCalculator.h"
#include "RooStats/SimpleInterval.h"
#include "TCanvas.h"

using namespace RooFit;
using namespace RooStats;

bool useBkg = true;
double confLevel = 0.90;

RooWorkspace *w = new RooWorkspace("w");
w->factory("SUM::pdf(s[0.001,15]*Uniform(x[0,1]),b[1,0,2]*Uniform(x))");
w->factory("Gaussian::prior_b(b,1,1)");
w->factory("PROD::model(pdf,prior_b)");
RooAbsPdf *model = w->pdf("model"); // pdf*priorNuisance
RooArgSet nuisanceParameters(*(w->var("b")));

RooAbsRealLValue *POI = w->var("s");
RooAbsPdf *priorPOI = (RooAbsPdf *)w->factory("Uniform::priorPOI(s)");
RooAbsPdf *priorPOI2 = (RooAbsPdf *)w->factory("GenericPdf::priorPOI2('1/sqrt(@0)',s)");

w->factory("n[3]"); // observed number of events

RooDataSet data("data", "", RooArgSet(*(w->var("x")), *(w->var("n"))), "n");
data.add(RooArgSet(*(w->var("x"))), w->var("n")->getVal());

RooMsgService::instance().setGlobalKillBelow(RooFit::FATAL);

RooArgSet *nuisPar = 0;
if (useBkg)
   nuisPar = &nuisanceParameters;

double size = 1. - confLevel;
std::cout << "\nBayesian Result using a Flat prior " << std::endl;
BayesianCalculator bcalc(data, *model, RooArgSet(*POI), *priorPOI, nuisPar);
bcalc.SetTestSize(size);
SimpleInterval *interval = bcalc.GetInterval();
double cl = bcalc.ConfidenceLevel();
std::cout << cl << "% CL central interval: [ " << interval->LowerLimit() << " - " << interval->UpperLimit()
          << " ] or " << cl + (1. - cl) / 2 << "% CL limits\n";
RooPlot *plot = bcalc.GetPosteriorPlot();
TCanvas *c1 = new TCanvas("c1", "Bayesian Calculator Result");
c1->Divide(1, 2);
c1->cd(1);
plot->Draw();
c1->Update();

std::cout << "\nBayesian Result using a 1/sqrt(s) prior  " << std::endl;
BayesianCalculator bcalc2(data, *model, RooArgSet(*POI), *priorPOI2, nuisPar);
bcalc2.SetTestSize(size);
SimpleInterval *interval2 = bcalc2.GetInterval();
cl = bcalc2.ConfidenceLevel();
std::cout << cl << "% CL central interval: [ " << interval2->LowerLimit() << " - " << interval2->UpperLimit()
          << " ] or " << cl + (1. - cl) / 2 << "% CL limits\n";

RooPlot *plot2 = bcalc2.GetPosteriorPlot();
c1->cd(2);
plot2->Draw();
gPad->SetLogy();
c1->Update();

gROOT->GetListOfCanvases()->Draw()