From 90869af8300683dcc8eedf909fe908c4a182789c Mon Sep 17 00:00:00 2001
From: Lorenzo Moneta <Lorenzo.Moneta@cern.ch>
Date: Tue, 24 Apr 2012 16:41:46 +0000
Subject: [PATCH] use noRounding for the Poisson of the sidebands since the
noff value can be in some cause non-integer (i.e. be interpreted as a Gamma
constraint)
git-svn-id: http://root.cern.ch/svn/root/trunk@43932 27541ba8-7e3a-0410-8455-c3a389f83636
---
roofit/roostats/src/NumberCountingPdfFactory.cxx | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/roofit/roostats/src/NumberCountingPdfFactory.cxx b/roofit/roostats/src/NumberCountingPdfFactory.cxx
index a4214272113..462682ba584 100644
--- a/roofit/roostats/src/NumberCountingPdfFactory.cxx
+++ b/roofit/roostats/src/NumberCountingPdfFactory.cxx
@@ -133,8 +133,10 @@ void NumberCountingPdfFactory::AddModel(Double_t* sig,
RooPoisson* sigRegion =
new RooPoisson(("sigRegion"+str.str()).c_str(),("sigRegion"+str.str()).c_str(), *x,*splusb);
+
+ //LM: need to set noRounding since y can take non integer values
RooPoisson* sideband =
- new RooPoisson(("sideband"+str.str()).c_str(),("sideband"+str.str()).c_str(), *y,*bTau);
+ new RooPoisson(("sideband"+str.str()).c_str(),("sideband"+str.str()).c_str(), *y,*bTau,true);
likelihoodFactors.Add(sigRegion);
likelihoodFactors.Add(sideband);
@@ -245,7 +247,11 @@ void NumberCountingPdfFactory::AddData(Double_t* mainMeas,
std::stringstream str;
str<<"_"<<i;
- Double_t _tau = 1./back[i]/back_syst[i]/back_syst[i];
+ //Double_t _tau = 1./back[i]/back_syst[i]/back_syst[i];
+ // LM: compute tau correctly for the Gamma distribution : mode = tau*b and variance is (tau*b+1)
+ Double_t err = back_syst[i];
+ Double_t _tau = (1.0 + sqrt(1 + 4 * err * err))/ (2. * err * err)/ back[i];
+
RooRealVar* tau = SafeObservableCreation(ws, ("tau"+str.str()).c_str(), _tau );
oocoutW(ws,ObjectHandling) << "NumberCountingPdfFactory: changed value of " << tau->GetName() << " to " << tau->getVal() <<
--
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