[ROOT] Re: Filling hosto in subroutines

From: Rene Brun (Rene.Brun@cern.ch)
Date: Fri Oct 17 2003 - 18:39:36 MEST


Hi Elena,

It looks like your histograms TH1F *f and *g are not named "f" and "g".
When doing t->Draw("p2.pt>>g"), ROOT will fill an histogram named "g".
If no histogram named "g" exists, one will be automatically created.


Rene Brun

 On 
Fri, 17 Oct 2003, Elena Vataga wrote:

> Hello, rooters!
> 
> 
> Could you, please, give me an advise on the following:
> 
> I created function inside my root macro which essentialy
> do the following:
> 
> void make_histo(TChain *t ,  TH1F* g, TH1F* b, TCut CUT ) {
>   t->Draw("p2.pt>>g");
>   t->Draw("p2.pt>>b",CUT);
>   g->Sumw2();
>   b->Sumw2();
> }
> 
> Histogram I am getting on return are empty.
> I cannot simply make:
> 
>  t->Draw("p2.pt>>htemp");
>  TH1F *g = (TH1F*)htemp->Clone("g")
> because I am using non-equidistant binning and need to pass
> booked histo into subroutine.
> 
> Any idea how to make it work?
> 
>         Thank you in advance,
>                         Elena
> 



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