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// $Id: MathUtils.cc,v 1.11 2009/11/04 12:44:33 loizides Exp $
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#include "MitCommon/MathTools/interface/MathUtils.h"
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#include <TError.h>
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#include <TH1D.h>
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#include <TGraphAsymmErrors.h>
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#include "PhysicsTools/RooStatsCms/interface/ClopperPearsonBinomialInterval.h"
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#include "PhysicsTools/RooStatsCms/interface/FeldmanCousinsBinomialInterval.h"
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ClassImp(mithep::MathUtils)
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using namespace mithep;
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//--------------------------------------------------------------------------------------------------
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Double_t MathUtils::AddInQuadrature(Double_t a, Double_t b)
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{
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// Add quantities in quadrature.
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return(TMath::Sqrt(a*a + b*b));
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}
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//--------------------------------------------------------------------------------------------------
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void MathUtils::CalcRatio(Double_t n1, Double_t n2, Double_t &r, Double_t &rlow, Double_t &rup, Int_t type = 0)
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{
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// Calculate ratio and lower/upper errors from given values using various methods, dependent on type:
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// 0: Bayes
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// 1: Feldman-Cousins
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// 2: Clopper-Pearson
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if (n1>n2) {
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Error("CalcRatio", "First value should be smaller than second: %f > %f", n1, n2);
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r = n1/n2;
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rlow = 0;
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rup = 0;
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return;
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}
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if (n2 >= 1) {
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if (type == 1) {
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//compute errors using Feldman-Cousins
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r = double(n1) / double(n2);
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FeldmanCousinsBinomialInterval fc;
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const double alpha = (1-0.682);
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fc.init(alpha);
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fc.calculate(n1, n2);
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rlow = r - fc.lower();
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rup = fc.upper() - r;
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} else if (type == 2) {
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//compute errors using Clopper-Pearson
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r = double(n1) / double(n2);
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ClopperPearsonBinomialInterval cp;
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const double alpha = (1-0.682);
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cp.init(alpha);
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cp.calculate(n1, n2);
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rlow = r - cp.lower();
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rup = cp.upper() - r;
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} else {
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//compute using Bayes
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TH1D h1("dummy1","",1,1,2);
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h1.SetBinContent(1,n1);
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TH1D h2("dummy2","",1,1,2);
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h2.SetBinContent(1,n2);
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TGraphAsymmErrors g;
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g.BayesDivide(&h1,&h2);
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r = g.GetY()[0];
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rup = g.GetErrorYhigh(0);
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rlow = g.GetErrorYlow(0);
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}
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} else {
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r = 0;
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rlow = 0;
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rup = 0;
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}
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}
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//--------------------------------------------------------------------------------------------------
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Double_t MathUtils::DeltaPhi(Double_t phi1, Double_t phi2)
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{
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// Compute DeltaPhi between two given angles. Results is in [-pi/2,pi/2].
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Double_t dphi = phi1-phi2;
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while (dphi > TMath::Pi())
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dphi -= TMath::TwoPi();
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while (dphi <= -TMath::Pi())
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dphi += TMath::TwoPi();
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return(dphi);
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}
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//--------------------------------------------------------------------------------------------------
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Double_t MathUtils::DeltaR(Double_t phi1, Double_t eta1, Double_t phi2, Double_t eta2)
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{
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// Compute DeltaR between two given points in the eta/phi plane.
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Double_t dR = TMath::Sqrt(DeltaR2(phi1,eta1,phi2,eta2));
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return(dR);
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}
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//--------------------------------------------------------------------------------------------------
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Double_t MathUtils::DeltaR2(Double_t phi1, Double_t eta1, Double_t phi2, Double_t eta2)
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{
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// Compute DeltaR between two given points in the eta/phi plane.
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Double_t dphi = DeltaPhi(phi1, phi2);
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Double_t deta = eta1-eta2;
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Double_t dR = dphi*dphi + deta*deta;
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return(dR);
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}
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//--------------------------------------------------------------------------------------------------
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Double_t MathUtils::Eta2Theta(Double_t eta)
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{
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// Compute theta from given eta value.
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return 2.*TMath::ATan(exp(-eta));
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}
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//--------------------------------------------------------------------------------------------------
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Double_t MathUtils::Theta2Eta(Double_t theta)
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{
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// Compute eta from given theta value.
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return -TMath::Log(TMath::Tan(theta/2.));
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}
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