TH2D - FitSlices not generating histograms

ROOT
1

Dear all,

I have the following piece of code that should extract a 2D histogram (“hJER_per_energy” --> hJER) from a list of files, and perform a fit on the 1D projections of these histograms. I can fit these 1D histograms, and get the constant/mean/sigma values printed. I cannot get the 1D histograms that should be created with the fit.

Below is the macro.

{
   // Step 1 - open Root files and retrieve 2D histograms.

   TString date = "20150107_had_em_jets"; TString numb = "1000000"; TString suffix = "_13_1_irJ.root";	// Hardest gen jet matched to closest (phi) det jet. 
   std::vector<TString> filenames;
   std::vector<TString> legendEntries;
   std::vector<int>     colours;

     filenames.push_back("LoopRootFiles/" + date + "_Output_JetAnalyzer_radii_GEN_ak3_DET_ak3_margin_0.500000_" + numb + "_Pythia6_Z2star_Default_varyR_CastorTree_MC_7TeV_42X_53XRECOwithCorrector" + suffix);
     legendEntries.push_back("(ak3) - (ak3)");

   /* Open files */

   TFile *_file0 = TFile::Open( filenames[0], "Read");

   /* Extract 2D  histo */

   TH2D *hJER = (TH2D*)_file0->Get("hJER_per_energy");    

   hJER->FitSlicesY(0,0,-1,10,"");
   hJER->Draw("colz");   

   hJER_1->Draw();
}

The last line results in error:

[color=#BF0000]Error: Symbol hJER_1 is not defined in current scope (tmpfile):1:
Error: Failed to evaluate hJER_1->Draw()
*** Interpreter error recovered ***[/color]

If I add

before drawing hJER_1, I get:

[color=#BF0000]Error: illegal pointer to class object hJER_1 0x0 1390 (tmpfile):1:
*** Interpreter error recovered ***[/color]

Could you please share your insights in this problem? Thanks!
Alex

2

Hi Alex,

Could you post also your ROOT file, to let us try?

Cheers, Bertrand.

3

Yes, of course. Be aware that in the code it will look for the file in directory LoopRootFiles, so edit that out.
20150107_had_em_jets_Output_JetAnalyzer_radii_GEN_ak3_DET_ak3_margin_0.500000_1000000_Pythia6_Z2star_Default_varyR_CastorTree_MC_7TeV_42X_53XRECOwithCorrector_13_1_irJ.root (229 KB)

4

Thanx Alex.

So replace:

hJER_1->Draw();By: hJER_per_energy_1->Draw(); Since the variable name is created with the histogram name (sorry to not have noticed that at first glance…)

Cheers, Bertrand.

5

Aha, that explains! Thanks a lot for the help! :smiley: