Hi Ilia,
I suggest you read page 88 of the ROOT Users Guide, section
"Resetting the Interpreter Environment"
gROOT->Reset deletes all global variables and definitions. Think to what
will happen if you use global variables in your named scripts.
In general, we recommend to use named scripts as in standard C++ and to follow
the usual C++ scoping rules. Unnamed scripts are OK to execute small tasks.
After execution of an unnamed script, all variables created in the script
are still accessible at the command line.
Rene Brun
Ilia Ravinovich wrote:
>
> On Tue, 7 Aug 2001, Rene Brun wrote:
>
> Dear Rene,
>
> Just saw your mail to Tomasso.
>
> > Hi Tommaso,
> >
> > Variables in a TNtuple are of type Float_t not Double_t.
> > You have two other problems in your script
> > - never use gROOT->Reset() in a named macro
>
> Why, what could be a problem?
>
> Thanks,
>
> Ilia
>
> > - the loop index starts at 0, not 1
> >
> > You have 3 ways (at least) to check the content of your ntuple.
> > - using teh browser, double click on your variable "p"
> > - use nf->Show(ki) to dump the values of entry ki
> > - use nf->Scan();
> >
> > Rene Brun
> >
> > Tommaso Chiarusi wrote:
> > >
> > > Hello rooters,
> > >
> > > According to the userguide, I wrote the following:
> > > Note:
> > > 1. "vario.root" is the root file in which I have stored my ntuple.
> > > 2. "front" is the name of my ntuple (in "vario.root" there are many
> > > other ntuples!).
> > > 3. "p" is the variable that I want to plot. ("p" is either the name of
> > > the TLeaf inside the ntuple "front" and of the variable the histogram I
> > > fill with)
> > >
> > > The problem I get is that I actually do NOT Get the Entry value, but
> > > something like 5.30784e-315!!!!!
> > >
> > > Thank you very much!
> > >
> > > void plot()
> > > {
> > > gROOT->Reset();
> > >
> > > TFile *f = new TFile("vario.root");
> > > TNtuple *nf = (TNtuple*)f->Get("front");
> > >
> > >
> > > Int_t entries = (Int_t)nf->GetEntries();
> > > cout<<"Number of Entries: "<<entries<< endl;
> > >
> > >
> > > Double_t p=0;
> > > nf->SetBranchAddress("p",&p);
> > >
> > > TH1F *htp = new TH1F("htp","p",100,0,10);
> > >
> > > for (Int_t ki=1;ki<entries;ki++)
> > > {
> > > nf->GetEntry(ki);
> > > htp->Fill(p);
> > > }
> > >
> > > TCanvas *c1 = new TCanvas("c1", "c1",515,210,540,376);
> > > c1->Draw();
> > > htp->Draw();
> > >
> > > //
> > > }
> > >
> > > Tommaso
> >
>
> ************************************************************************
> * *
> * Ilia Ravinovich *
> * Department of Particle Physics PPE Division *
> * Weizmann Institute of Science Bld 892, 1D-015 *
> * Rehovot 76100 CERN, 1211 Geneva *
> * ISRAEL Switzerland *
> * *
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