Re: How to get an Histogram ?

Hi Jordi, you seem to have a typo at this line:

>> HangingTree->Draw(raw+">>histo");

but anyway, if you have a variable called x in your TTree, you should be able to retrieve the histogram this way:

HangingTree->Draw("x>>histo");
TH1* h = (TH1*)gDirectory->Get("histo")

Cheers
Marcelo

2011/9/7 Jordi Nadal <jnadal_at_ifae.es>

> Hi Suvayu,
>
> Is this done correctly?
>
> [jnadal_at_at305 JetFitter]$ root PSE/JO_muon_PSE_RbFree/sumRootFile.root
> Welcome to the ATLAS rootlogon.C
> root [0]
> Attaching file PSE/JO_muon_PSE_RbFree/sumRootFile.root as _file0...
> root [1] gROOT->FindObject("Wjets_HFC_4ex")
> (const class TObject*)0x0
> root [2] .ls
> TFile** PSE/JO_muon_PSE_RbFree/sumRootFile.root
> TFile* PSE/JO_muon_PSE_RbFree/sumRootFile.root
> KEY: TTree HangingTree;1 no lemons at that tree
> root [3] TH1F *Wjets_HFC = (TH1F*) gROOT->FindObject("Wjets_HFC_4ex")
> root [4] Wjets_HFC->GetMean
> GetMean
> GetMeanError
> root [4] Wjets_HFC->GetMean()
> Error: illegal pointer to class object Wjets_HFC 0x0 550 (tmpfile):1:
> *** Interpreter error recovered ***
> root [5]
>
> Thanks!
>
> Jordi
> On Sep 7, 2011, at 5:49 PM, suvayu ali wrote:
>
> > On Wed, Sep 7, 2011 at 5:01 PM, Jordi Nadal <jnadal_at_ifae.es> wrote:
> >> Hello experts,
> >>
> >> Basically what I want to do is:
> >>
> >> TFile *file = TFile::Open("PSE/JO_muon_PSE_RbFree/sumRootFile.root");
> >> TTree* HangingTree = (TTree*) file->Get("HangingTree");
> >> HangingTree->Draw(raw+">>histo");
> >>
> >> is there a better way to "get " this histo?
> >>
> >> I would like to do is histo->GetMean() and doing it like above I get
> wrong numbers…
> >>
> >
> > This should work:
> >
> > TH1D *histo = (TH1D*) gROOT->FindObject("histo");
> > histo->GetMean();
> >
> >
> > --
> > Suvayu
> >
> > Open source is the future. It sets us free.
>
>
Received on Wed Sep 07 2011 - 19:23:32 CEST