How to calculate the standard deviation over a list of histograms existing in one root file?

Baktash_Amini · August 27, 2021, 12:30pm

Hello, I have a list of histograms in a single root file. I want to compute the standard deviation on a particular bin of these histograms. Could you please guide me how to proceed?

I guess I need to loop over all the histograms and then I can compute the standard deviation on that bin.

Thanks in advance.

void anal_hist_result(string ttbarMC="ppepembbar_4FNS_LO_all_results"){
    TFile *file        = TFile::Open("ppepembbar_4FNS_LO_all_results.root");

    TH1F *h0 = (TH1F*)file->Get("AFB_Mll_0"); 
    TH1F *h1 = (TH1F*)file->Get("AFB_Mll_1"); 
    TH1F *h2 = (TH1F*)file->Get("AFB_Mll_2"); 
    TH1F *h3 = (TH1F*)file->Get("AFB_Mll_3"); 
    TH1F *h4 = (TH1F*)file->Get("AFB_Mll_4"); 
    TH1F *h5 = (TH1F*)file->Get("AFB_Mll_5"); 
    TH1F *h6 = (TH1F*)file->Get("AFB_Mll_6"); 
    TH1F *h7 = (TH1F*)file->Get("AFB_Mll_7"); 
    TH1F *h8 = (TH1F*)file->Get("AFB_Mll_8"); 
    TH1F *h9 = (TH1F*)file->Get("AFB_Mll_9"); 
    TH1F *h10 = (TH1F*)file->Get("AFB_Mll_10"); 
    TH1F *h11 = (TH1F*)file->Get("AFB_Mll_11"); 
    TH1F *h12 = (TH1F*)file->Get("AFB_Mll_12"); 
    TH1F *h13 = (TH1F*)file->Get("AFB_Mll_13"); 
    TH1F *h14 = (TH1F*)file->Get("AFB_Mll_14"); 
    TH1F *h15 = (TH1F*)file->Get("AFB_Mll_15"); 
    TH1F *h16 = (TH1F*)file->Get("AFB_Mll_16"); 
    TH1F *h17 = (TH1F*)file->Get("AFB_Mll_17"); 
    TH1F *h18 = (TH1F*)file->Get("AFB_Mll_18"); 
    TH1F *h19 = (TH1F*)file->Get("AFB_Mll_19"); 
    TH1F *h20 = (TH1F*)file->Get("AFB_Mll_20"); 
    TH1F *h21 = (TH1F*)file->Get("AFB_Mll_21"); 
    TH1F *h22 = (TH1F*)file->Get("AFB_Mll_22"); 
    TH1F *h23 = (TH1F*)file->Get("AFB_Mll_23"); 
    TH1F *h24 = (TH1F*)file->Get("AFB_Mll_24");
    TH1F *h25 = (TH1F*)file->Get("AFB_Mll_25"); 
    TH1F *h26 = (TH1F*)file->Get("AFB_Mll_26"); 
    TH1F *h27 = (TH1F*)file->Get("AFB_Mll_27"); 
    TH1F *h28 = (TH1F*)file->Get("AFB_Mll_28"); 
    TH1F *h29 = (TH1F*)file->Get("AFB_Mll_29"); 
    TH1F *h30 = (TH1F*)file->Get("AFB_Mll_30"); 
    TH1F *h31 = (TH1F*)file->Get("AFB_Mll_31");    
    TH1F *h32 = (TH1F*)file->Get("AFB_Mll_32"); 
    TH1F *h33 = (TH1F*)file->Get("AFB_Mll_33"); 
    TH1F *h34 = (TH1F*)file->Get("AFB_Mll_34"); 
    TH1F *h35 = (TH1F*)file->Get("AFB_Mll_35"); 
    TH1F *h36 = (TH1F*)file->Get("AFB_Mll_36"); 
    TH1F *h37 = (TH1F*)file->Get("AFB_Mll_37"); 
    TH1F *h38 = (TH1F*)file->Get("AFB_Mll_38"); 
    TH1F *h39 = (TH1F*)file->Get("AFB_Mll_39"); 
    TH1F *h40 = (TH1F*)file->Get("AFB_Mll_40"); 
    TH1F *h41 = (TH1F*)file->Get("AFB_Mll_41"); 
    TH1F *h42 = (TH1F*)file->Get("AFB_Mll_42"); 
    TH1F *h43 = (TH1F*)file->Get("AFB_Mll_43"); 
    //TH1F *h44 = (TH1F*)file->Get("AFB_Mll_44"); 
    TH1F *h45 = (TH1F*)file->Get("AFB_Mll_45"); 
    TH1F *h46 = (TH1F*)file->Get("AFB_Mll_46"); 
    TH1F *h47 = (TH1F*)file->Get("AFB_Mll_47"); 
    TH1F *h48 = (TH1F*)file->Get("AFB_Mll_48"); 
    TH1F *h49 = (TH1F*)file->Get("AFB_Mll_49"); 
    TH1F *h50 = (TH1F*)file->Get("AFB_Mll_50"); 
    TH1F *h51 = (TH1F*)file->Get("AFB_Mll_51"); 
    TH1F *h52 = (TH1F*)file->Get("AFB_Mll_52"); 
    TH1F *h53 = (TH1F*)file->Get("AFB_Mll_53"); 
    TH1F *h54 = (TH1F*)file->Get("AFB_Mll_54"); 
    TH1F *h55 = (TH1F*)file->Get("AFB_Mll_55"); 
    TH1F *h56 = (TH1F*)file->Get("AFB_Mll_56"); 
    TH1F *h57 = (TH1F*)file->Get("AFB_Mll_57"); 
    TH1F *h58 = (TH1F*)file->Get("AFB_Mll_58"); 
    TH1F *h59 = (TH1F*)file->Get("AFB_Mll_59"); 
    TH1F *h60 = (TH1F*)file->Get("AFB_Mll_60"); 
    TH1F *h61 = (TH1F*)file->Get("AFB_Mll_61"); 
    TH1F *h62 = (TH1F*)file->Get("AFB_Mll_62"); 
    TH1F *h63 = (TH1F*)file->Get("AFB_Mll_63");
    TH1F *h64 = (TH1F*)file->Get("AFB_Mll_64"); 
    TH1F *h65 = (TH1F*)file->Get("AFB_Mll_65"); 
	TH1F *h66 = (TH1F*)file->Get("AFB_Mll_66");
    TH1F *h67 = (TH1F*)file->Get("AFB_Mll_67"); 
    TH1F *h68 = (TH1F*)file->Get("AFB_Mll_68"); 
    TH1F *h69 = (TH1F*)file->Get("AFB_Mll_69"); 
    TH1F *h70 = (TH1F*)file->Get("AFB_Mll_70"); 
    TH1F *h71 = (TH1F*)file->Get("AFB_Mll_71"); 
    TH1F *h72 = (TH1F*)file->Get("AFB_Mll_72"); 
    TH1F *h73 = (TH1F*)file->Get("AFB_Mll_73"); 
    TH1F *h74 = (TH1F*)file->Get("AFB_Mll_74"); 
    TH1F *h75 = (TH1F*)file->Get("AFB_Mll_75"); 
    TH1F *h76 = (TH1F*)file->Get("AFB_Mll_76"); 
    TH1F *h77 = (TH1F*)file->Get("AFB_Mll_77"); 
    TH1F *h78 = (TH1F*)file->Get("AFB_Mll_78"); 
    TH1F *h79 = (TH1F*)file->Get("AFB_Mll_79"); 
    TH1F *h80 = (TH1F*)file->Get("AFB_Mll_80"); 
    TH1F *h81 = (TH1F*)file->Get("AFB_Mll_81"); 
    TH1F *h82 = (TH1F*)file->Get("AFB_Mll_82"); 
    TH1F *h83 = (TH1F*)file->Get("AFB_Mll_83"); 
    TH1F *h84 = (TH1F*)file->Get("AFB_Mll_84"); 
    TH1F *h85 = (TH1F*)file->Get("AFB_Mll_85"); 
    TH1F *h86 = (TH1F*)file->Get("AFB_Mll_86"); 
    TH1F *h87 = (TH1F*)file->Get("AFB_Mll_87"); 
    TH1F *h88 = (TH1F*)file->Get("AFB_Mll_88"); 
    TH1F *h89 = (TH1F*)file->Get("AFB_Mll_89"); 
    TH1F *h90 = (TH1F*)file->Get("AFB_Mll_90"); 
    TH1F *h91 = (TH1F*)file->Get("AFB_Mll_91"); 
    TH1F *h92 = (TH1F*)file->Get("AFB_Mll_92"); 
    TH1F *h93 = (TH1F*)file->Get("AFB_Mll_93"); 
    TH1F *h94 = (TH1F*)file->Get("AFB_Mll_94"); 
    TH1F *h95 = (TH1F*)file->Get("AFB_Mll_95"); 
    TH1F *h96 = (TH1F*)file->Get("AFB_Mll_96"); 
    TH1F *h97 = (TH1F*)file->Get("AFB_Mll_97"); 
    TH1F *h98 = (TH1F*)file->Get("AFB_Mll_98"); 
    TH1F *h99 = (TH1F*)file->Get("AFB_Mll_99"); 
    TH1F *h100 = (TH1F*)file->Get("AFB_Mll_100"); 
    TH1F *h101 = (TH1F*)file->Get("AFB_Mll_101"); 
    TH1F *h102 = (TH1F*)file->Get("AFB_Mll_102"); 
    TH1F *h103 = (TH1F*)file->Get("AFB_Mll_103"); 
    TH1F *h104 = (TH1F*)file->Get("AFB_Mll_104"); 
    TH1F *h105 = (TH1F*)file->Get("AFB_Mll_105"); 
    TH1F *h106 = (TH1F*)file->Get("AFB_Mll_106"); 
    TH1F *h107 = (TH1F*)file->Get("AFB_Mll_107"); 
    TH1F *h108 = (TH1F*)file->Get("AFB_Mll_108"); 
    TH1F *h109 = (TH1F*)file->Get("AFB_Mll_109"); 
    TH1F *h110 = (TH1F*)file->Get("AFB_Mll_110"); 
    TH1F *h111 = (TH1F*)file->Get("AFB_Mll_111"); 
    TH1F *h112 = (TH1F*)file->Get("AFB_Mll_112"); 
    TH1F *h113 = (TH1F*)file->Get("AFB_Mll_113"); 
    TH1F *h114 = (TH1F*)file->Get("AFB_Mll_114"); 
    TH1F *h115 = (TH1F*)file->Get("AFB_Mll_115"); 
    TH1F *h116 = (TH1F*)file->Get("AFB_Mll_116"); 
    TH1F *h117 = (TH1F*)file->Get("AFB_Mll_117"); 
    TH1F *h118 = (TH1F*)file->Get("AFB_Mll_118"); 
    TH1F *h119 = (TH1F*)file->Get("AFB_Mll_119"); 
    TH1F *h120 = (TH1F*)file->Get("AFB_Mll_120"); 
    TH1F *h121 = (TH1F*)file->Get("AFB_Mll_121"); 
    TH1F *h122 = (TH1F*)file->Get("AFB_Mll_122"); 
    TH1F *h123 = (TH1F*)file->Get("AFB_Mll_123"); 
    TH1F *h124 = (TH1F*)file->Get("AFB_Mll_124"); 
    TH1F *h125 = (TH1F*)file->Get("AFB_Mll_125"); 
    TH1F *h126 = (TH1F*)file->Get("AFB_Mll_126"); 
    TH1F *h127 = (TH1F*)file->Get("AFB_Mll_127"); 
    TH1F *h128 = (TH1F*)file->Get("AFB_Mll_128"); 
    TH1F *h129 = (TH1F*)file->Get("AFB_Mll_129"); 
    TH1F *h130 = (TH1F*)file->Get("AFB_Mll_130"); 
    TH1F *h131 = (TH1F*)file->Get("AFB_Mll_131"); 
    TH1F *h132 = (TH1F*)file->Get("AFB_Mll_132"); 
    TH1F *h133 = (TH1F*)file->Get("AFB_Mll_133"); 
    TH1F *h134 = (TH1F*)file->Get("AFB_Mll_134"); 
    TH1F *h135 = (TH1F*)file->Get("AFB_Mll_135"); 
    TH1F *h136 = (TH1F*)file->Get("AFB_Mll_136"); 
    TH1F *h137 = (TH1F*)file->Get("AFB_Mll_137"); 
    TH1F *h138 = (TH1F*)file->Get("AFB_Mll_138"); 
    TH1F *h139 = (TH1F*)file->Get("AFB_Mll_139"); 
    TH1F *h140 = (TH1F*)file->Get("AFB_Mll_140"); 
    TH1F *h141 = (TH1F*)file->Get("AFB_Mll_141"); 
    TH1F *h142 = (TH1F*)file->Get("AFB_Mll_142"); 
    TH1F *h143 = (TH1F*)file->Get("AFB_Mll_143"); 
    TH1F *h144 = (TH1F*)file->Get("AFB_Mll_144"); 
  
   for (auto&& keyAsObj : file->GetListOfKeys()){
 auto key = (TKey*) keyAsObj;
 cout << key->GetName() << " " << key->GetClassName() << endl;

	}
}

Baktash_Amini · August 27, 2021, 12:32pm

I get this error when I run this code:
error: invalid range expression of type ‘TList '; did you mean to dereference it with '’?
for (auto&& keyAsObj : file->GetListOfKeys()){
^
*

Wile_E_Coyote · August 27, 2021, 4:44pm

Attach the “ppepembbar_4FNS_LO_all_results.root” file.

Baktash_Amini · August 28, 2021, 8:43am

The root file is on the farm and I do not have the permission to download it. But it contains all the histograms “AFB_Mll_num” I indicated in the code above. If you could guide me on what steps I should follow to obtain the standard deviation of all these histograms on that particular bin that would be a great help.

Baktash_Amini · August 28, 2021, 1:40pm

Thank you for you help.

I tried this, I got an empty histogram and this error: Error in TProfile::Add: Attempt to add a non-profile object.

void hist(){

TFile *f = TFile::Open(“ppepembbar_4FNS_LO_all_results.root”);
if ((!f) || f->IsZombie()) { delete f; return; }
gROOT->cd();
TProfile *hp = 0;
TH1 *h;
for (int i = 0; i < 145; i++) {
f->GetObject(TString::Format(“AFB_Mll_%d”, i), h);
if (h) {
if (!hp) {
TAxis *a = h->GetXaxis();
hp = new TProfile(“AFB_Mll_profile”, “AFB Mll profile;X;Y”,
a->GetNbins(), a->GetXmin(), a->GetXmax());
if (! hp->GetSumw2N()) hp->Sumw2(kTRUE);
}
hp->Add(h);
delete h;
}
}
delete f;
if (hp) hp->Draw();
}

Baktash_Amini · August 28, 2021, 1:42pm

Since I have 144 histograms, I changed 199 to 145 in the argument of for loop.

Wile_E_Coyote · August 28, 2021, 1:52pm

Try:

{
  TFile *f = TFile::Open("ppepembbar_4FNS_LO_all_results.root");
  if ((!f) || f->IsZombie()) { delete f; return; }
  gROOT->cd();
  TProfile *hp = 0;
  for (int i = 0; i < 199; i++) {
    TH1 *h; f->GetObject(TString::Format("AFB_Mll_%d", i), h);
    if (h) {
      TAxis *a = h->GetXaxis();
      if (!hp) {
        // ... assuming all "AFB_Mll_*" are "akin" fix bin sizes histograms ...
        hp = new TProfile("AFB_Mll_profile", "AFB Mll profile;X;Y",
                          a->GetNbins(), a->GetXmin(), a->GetXmax(),
                          ""); // e.g., "", "s", "i" or "g"
        if (! hp->GetSumw2N()) hp->Sumw2(kTRUE);
      }
      for (int j = 0; j <= a->GetNbins() + 1; j++)
        hp->Fill(a->GetBinCenter(j), h->GetBinContent(j), h->GetBinError(j));
      delete h;
    }
  }
  delete f;
  if (hp) hp->Draw();
}

Baktash_Amini · August 28, 2021, 1:57pm

Thank you very much it worked fine. Now if I want to compute the standard deviation on bin 6 then I delete the for loop:

void hist(string ttbarMC=“ppepembbar_4FNS_LO_all_results”){
TFile *f = TFile::Open(“ppepembbar_4FNS_LO_all_results.root”);
if ((!f) || f->IsZombie()) { delete f; return; }
gROOT->cd();
TProfile *hp = 0;
TH1 *h;
for (int i = 0; i < 199; i++) {
f->GetObject(TString::Format(“AFB_Mll_%d”, i), h);
if (h) {
TAxis *a = h->GetXaxis();
if (!hp) {
hp = new TProfile(“AFB_Mll_profile”, “AFB Mll profile;X;Y”,
a->GetNbins(), a->GetXmin(), a->GetXmax());
if (! hp->GetSumw2N()) hp->Sumw2(kTRUE);
}

    hp->Fill(a->GetBinCenter(6), h->GetBinContent(6), h->GetBinError(6));
  delete h;
}

}
delete f;
if (hp) hp->Draw();
}

Wile_E_Coyote · August 28, 2021, 2:00pm

From the TProfile description, I assume you want to retrieve its bin 6 (e.g., contents and error).

Baktash_Amini · August 28, 2021, 2:02pm

Yes, I want to retrieve its bin 6. The way I made changes in the code you wrote is correct to compute the standard deviation on bin 6?

Wile_E_Coyote · August 28, 2021, 2:08pm

It makes no sense to create and fill a TProfile just to get a single bin. You can loop over all TH1 histograms and calculate this single value yourself (e.g., from “h->GetBinContent(6)” and “h->GetBinError(6)”).

Baktash_Amini · August 28, 2021, 2:12pm

Yeah but I could not loop over all these histograms. Can you show me how to loop over all histograms?

Wile_E_Coyote · August 28, 2021, 2:14pm

My “example” macro loops over all “AFB_Mll_*” histograms.

{
  TFile *f = TFile::Open("ppepembbar_4FNS_LO_all_results.root");
  if ((!f) || f->IsZombie()) { delete f; return; }
  for (int i = 0; i < 199; i++) {
    TH1 *h; f->GetObject(TString::Format("AFB_Mll_%d", i), h);
    if (h) {
      std::cout << i << " " << h->GetBinContent(6) << " " << h->GetBinError(6) << std::endl;
      delete h;
    }
  }
  delete f;
}

Baktash_Amini · August 28, 2021, 2:34pm

Thanks a lot for you help. In both cases, I obtained the same value for the standard deviation.

system · September 11, 2021, 2:34pm

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