new utility class for TRD PID (Alex W)
[u/mrichter/AliRoot.git] / TRD / AliTRDpidUtil.cxx
CommitLineData
0e60774c 1#include "TObject.h"
2#include "TMath.h"
3#include "TF1.h"
4#include "TH1F.h"
5#include "TGraph.h"
6#include "TGraphErrors.h"
7
8#include "AliLog.h"
9#include "Cal/AliTRDCalPID.h"
10#include "AliTRDpidUtil.h"
11
12ClassImp(AliTRDpidUtil)
13
14
15Float_t AliTRDpidUtil::fEleEffi = 0.9;
16
17//________________________________________________________________________
18AliTRDpidUtil::AliTRDpidUtil()
19 : TObject()
20 ,fCalcEleEffi(0.)
21 ,fPionEffi(-1.)
22 ,fError(-1.)
23 ,fThreshold(-1.)
24{
25 //
26 // Default constructor
27 //
28}
29
30
31
32//________________________________________________________________________
33void AliTRDpidUtil::CalculatePionEffi(TH1F* histo1, TH1F* histo2)
34// Double_t AliTRDpidUtil::GetError()
35{
36 //
37 // Calculates the pion efficiency
38 //
39
40 histo1 -> SetLineColor(kRed);
41 histo2 -> SetLineColor(kBlue);
42 AliInfo(Form("Histo1[%d] Histo2[%d]", (Int_t)histo1 -> GetEntries(), (Int_t)histo2 -> GetEntries()));
43 if(!(histo1 -> GetEntries() > 0 && histo2 -> GetEntries() > 0)){
44 AliWarning("Histo has no Entries !");
45 return;
46 }
47 histo1 -> Scale(1./histo1->GetEntries());
48 histo2 -> Scale(1./histo2->GetEntries());
49
50 Int_t abinE, bbinE, cbinE = -1;
51 Double_t aBinSumE, bBinSumE; // content of a single bin
52 Bool_t bFirst = 1; // checks if threshold is crossed for the first time
53 Double_t SumElecsE[kBins], SumPionsE[kBins]; // array of the integrated sum in each bin
54 memset(SumElecsE, 0, kBins*sizeof(Double_t));
55 memset(SumPionsE, 0, kBins*sizeof(Double_t));
56
57
58 // calculate electron efficiency of each bin
59 for (abinE = (histo1 -> GetNbinsX())-2; abinE >= 0; abinE--){
60 aBinSumE = 0;
61 aBinSumE = histo1 -> GetBinContent(abinE);
62
63 SumElecsE[abinE] = SumElecsE[abinE+1] + aBinSumE;
64 if((SumElecsE[abinE] >= fEleEffi) && (bFirst == 1)){
65 bFirst = 0;
66 cbinE = abinE;
67 fCalcEleEffi = (SumElecsE[cbinE]);
68 }
69 }
70
71 fThreshold = histo1 -> GetBinCenter(cbinE);
72
73 // calculate pion efficiency of each bin
74 for (bbinE = (histo2 -> GetNbinsX())-2; bbinE >= abinE; bbinE--){
75 bBinSumE = 0;
76 bBinSumE = histo2 -> GetBinContent(bbinE);
77
78 SumPionsE[bbinE] = SumPionsE[bbinE+1] + bBinSumE;
79 if(bbinE == cbinE){
80 fPionEffi = (SumPionsE[cbinE]);
81 }
82 }
83
84
85 // pion efficiency vs electron efficiency
86 TGraph *gEffis = new TGraph(kBins, SumElecsE, SumPionsE);
87
88 // use fit function to get derivate of the TGraph for error calculation
89 TF1 *f1 = new TF1("f1","[0]*x*x+[1]*x+[2]", fEleEffi-.05, fEleEffi+.05);
90 gEffis -> Fit("f1","Q","",fEleEffi-.05, fEleEffi+.05);
91 AliInfo(Form("Derivative at %4.2f : %f", fEleEffi, f1 -> Derivative(fEleEffi)));
92
93 // return the error of the pion efficiency
94 if(((1.-fPionEffi) < 0) || ((1.-fCalcEleEffi) < 0)){
95 AliWarning(" EleEffi or PioEffi > 1. Error can not be calculated. Please increase statistics or check your simulation!");
96 return;
97 }
98 fError = sqrt(((1/histo2 -> GetEntries())*fPionEffi*(1-fPionEffi))+((f1 -> Derivative(fEleEffi))*(f1 -> Derivative(fEleEffi))*(1/histo1 -> GetEntries())*fCalcEleEffi*(1-fCalcEleEffi)));
99}
100
101
102//__________________________________________________________________________
103Int_t AliTRDpidUtil::GetMomentumBin(Double_t p)
104{
105 //
106 // returns the momentum bin for a given momentum
107 //
108
109 Int_t pBin1 = -1; // check bin1
110 Int_t pBin2 = -1; // check bin2
111
112 if(p < 0) return -1; // return -1 if momentum < 0
113 if(p < AliTRDCalPID::GetMomentum(0)) return 0; // smallest momentum bin
114 if(p >= AliTRDCalPID::GetMomentum(AliTRDCalPID::kNMom-1)) return AliTRDCalPID::kNMom-1; // largest momentum bin
115
116
117 // calculate momentum bin for non extremal momenta
118 for(Int_t iMomBin = 1; iMomBin < AliTRDCalPID::kNMom; iMomBin++){
119 if(p < AliTRDCalPID::GetMomentum(iMomBin)){
120 pBin1 = iMomBin - 1;
121 pBin2 = iMomBin;
122 }
123 else
124 continue;
125
126 if(p - AliTRDCalPID::GetMomentum(pBin1) >= AliTRDCalPID::GetMomentum(pBin2) - p){
127 return pBin2;
128 }
129 else{
130 return pBin1;
131 }
132 }
133
134 return -1;
135}
136