2D TEfficiency

From: Simone Bifani <simone.bifani_at_cern.ch>
Date: Wed, 22 Dec 2010 09:36:50 +0100

  Dear ROOTers,

I am trying to use the TEfficiency class (ROOT 5.28.00) to parametrize a trigger efficiency as a function of two variables

Unfortunately there is no TEfficiency TH2 constructor such as

/ TEfficiency(const TH2& passed, const TH2& total)/

but I managed to use

/ TEfficiency(const char* name, const char* title, Int_t nbinsx,
Double_t xlow, Double_t xup, Int_t nbinsy, Double_t ylow, Double_t yup)/

Suppose hNL1 is the TH2D histogram corresponding to the "passed" events and hDL1 to the "total" ones, I tried the following:

/ TEfficiency *tEL1 = new TEfficiency("tEL1", "", hNL1->GetNbinsX(),

hNL1->GetXaxis()->GetXmin(), hNL1->GetXaxis()->GetXmax(), 
hNL1->GetNbinsY(), hNL1->GetYaxis()->GetXmin(), 
hNL1->GetYaxis()->GetXmax());
   for (Int_t i = 1; i <= hNL1->GetNbinsX(); ++i) {
     for (Int_t j = 1; j <= hNL1->GetNbinsY(); ++j) {
       tEL1->GetPassedHistogram()->SetBinContent(i, j, 
hNL1->GetBinContent(i, j));
       tEL1->GetTotalHistogram()->SetBinContent(i, j, 
hDL1->GetBinContent(i, j));
     }

   }
/

While using CINT everything is fine, if I try to compile this lines I get the following error

/ error: passing 'const TH1' as 'this' argument of 'virtual void
TH1::SetBinContent(Int_t, Int_t, Double_t)' discards qualifiers/

which as far as I can understand is due to the fact that GetPassedHistogram() and GetTotalHistogram() return a const object that I cannot modify

My first question is how can I solve this problem? How can I easily create a 2D TEfficiency starting from two TH2D histos?

Next, why there is no 2D TEfficiency constructor? Moreover, even if the TEfficiency class as it is now can be used to create 2D and 3D objects, why there is only a /GetEfficiency(Int_t bin)/ method and not /GetEfficiency(Int_t binx, Int_t biny)/ and
/GetEfficiency(Int_t binx, Int_t biny, Int_t binz)/ ones as well? I
know I can use /GetBin(Int_t binx, Int_t biny, Int_t binz)/ to retrieve the global bin number and this is working, but it would be handier

Last question, as I mentioned earlier when using CINT the lines I wrote are working but when I draw the 2D TEfficiency object as
/tEL1->Draw("colz")/ X and Y axis doesn't correspond to the created ones
according to hNL1 but both ranges goes from 0 to 1 How is that possible?

Thanks,
s.

Received on Wed Dec 22 2010 - 09:36:58 CET