Re: proj ntuple into predefined histogram

From: Dirk Meier (Dirk.Meier@cern.ch)
Date: Tue Aug 18 1998 - 22:34:17 MEST


On Tue, 18 Aug 1998, Stephen Bailey wrote:

> 
> Hi.
> 
> I'm trying to project an ntuple into a histogram which I
> defined so that I can control the number of bins used.
> e.g.
> 
>    TH1F h1 = new TH1F("blat", "quat", 20, 4.5, 6);
>    ntuple->Draw("m>>+h1", "(4.5<m)&&(m<6.0)");
>    h1->Draw();
> 
> I also tryed m>>h1, but the ntuple->Draw command always
> picks its own choice for number of bins and h1 always
> seems to remain empty.  If I don't predefine h1 then it
> gets created and properly filled but I don't have control
> over the number of bins.
> 
> Is there a way to do this easily (i.e. without looping
> trough the ntuple and filling the histogram event by event)?
> 
> Thanks.
> 
> Stephen Bailey
> 
> 
> 
> 
> 

Stephen,

it works with the following:

   TH1F h1 = new TH1F("blat", "quat", 20, 4.5, 6);
   ntuple->Draw("m>>blat");      // no limits necessary any more, use +
				//when you fill more events into blat
   h1->Draw();          // also blat->Draw()  draws h1


Dirk



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