RooFit: reading root histograms and trees from a root file

ROOT
1

Hi ROOTalkers,

I wanted to use RooFit to do maximum likelihood
fits of my histograms and tree variables but have
problems reading in my root file. I have checked
Roofit documentation, but the examples offered there
are too simple for my application.

  1. I am using root-5.22.00 version.

  2. First, I have a ROOT problem declaring the
    pointer to a histogram in *.root file and
    drawing that histogram. I can start ROOT
    interactively, start TBrowser and click on
    histogram and see that it is OK.

    But, in my macro, the following does not work:

    TFile f = new TFile(“run84101.root”);
    TH1F h1 = (TH1F) f->Get(“h1THRESHOLD_10”);
    TCanvas     c=new TCanvas(“PEN Maximum Likelihood Analysis”,“PEN Maximum Likelihood Analysis”,200,10,700,600);
    h1->Draw();
    c->Update();

    Reported error is:

Error: illegal pointer to class object h1 0x0 406 h_maxPEN.C:53:
*** Interpreter error recovered ***

My histogram "h1THRESHOLD_10" is in folder /histos/Check, so I tried
variations:

TFile input("/home/ef2p/pen08/maxlike/run84101.root");
input.cd("/histos/Check");  
TH1F *h1 = (TH1F*) f->Get("h1THRESHOLD_10");

but that produces the same "illegal pointer error". So, I am
stuck without sucessful input and cannot use RooFit.
  1. Second I try to read in a TTree that is in the same file run84101.root.
    I succeed in plotting two Tree variables with:

TFile f(“run84101.root”) ;
t1=(TTree ) gROOT->FindObject(“usertree”) ;
TCanvas c=new TCanvas(“PEN Maximum Likelihood Analysis”,“PEN Maximum Likelihood Analysis”,200,10,700,600);
c->Divide(1,2) ;
c->cd(1) ;
t1->Draw(“digi.t_pion”) ;
c->cd(2) ;
t1->Draw(“asum.csi_sum”) ;
c->Update();

But, the variables are in sub-sub-branches, so when I try to assocuate them with
RooDataSet, that fails:

RooRealVar asum.csi_sum(“asum.csi_sum”,“asum.csi_sum”,0,100) ;
RooRealVar digi.t_pion(“digi.t_pion”,“digi.t_pion”,200,640) ;
RooDataSet pen_emodel(“pen_emodel”,“pen_emodel”,RooArgSet(asum.csi_sum,digi.t_pion),Import(t1)) ;
RooPlot frame1=asum.csi_sum.frame(Title(“1L Energy”)) ;
pen_emodel.plotOn(frame1) ;

with error mesasages:

Error: Symbol asum is not defined in current scope t_maxPEN.C:55:
Error: Failed to evaluate asum.csi_sum
Error: Symbol digi is not defined in current scope t_maxPEN.C:55:
Error: Failed to evaluate digi.t_pion
*** Interpreter error recovered ***

Does that mean that I have to redefine/rewrite my Tree and that
Roofit cannot understand sub-branches or my syntax is wrong?

                                          Cheers, Emil

f1.ps (10.3 KB)
f2.ps (8.89 KB)
run84101.root (797 KB)

2

1:
TFolder folder = (TFolder)filepointer->GetKey(“histos”)->ReadObj()
TH1F h = (TH1F)folder->FindObject(“Check/h1THRESHOLD_10”)

works for me