Re: TTree::Draw() with weights

Nick van Eijndhoven (Nick@phys.uu.nl)
Thu, 12 Nov 1998 14:50:04 +0100

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Christoph Ernst wrote:
>
> Hello,
>
> Is there a simple way to rescale the y-axis of a TH1 when you plot it from
> TTree::Draw()?
> For example I want to draw a pt spectrum via tree->Draw("pt"). But as
> 1/pt * dN/dpt not just as dN/dpt.
> Also, I would like to plot histos from a Tree where each entry has a
> specific weight w (something like dw/dx). In a loop I would simply say
> h1->Fill(x_i, w_i);.
> But I cannot figure out how to do this in the nice way of TTree::Draw().
> If TTree::Draw() can't do it, what do you think is the best alternative?
>
> Greetings
> Christoph
>

Hi Christoph,
The way I always do this is :

tree->Draw("pt","1.*1./pt")

Cheers,

_/_/ _/ _/ _/_/_/_/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/_/ _/ _/_/ _/ _/ _/ _/ _/ _/ _/ _/_/_/_/ _/ _/

*----------------------------------------------------------------------* Dr. Nick van Eijndhoven Department of Subatomic Physics email : nick@phys.uu.nl Utrecht University / NIKHEF tel. +31-30-2532331 (direct) P.O. Box 80.000 tel. +31-30-2531492 (secr.) NL-3508 TA Utrecht fax. +31-30-2518689 The Netherlands WWW : http://www.phys.uu.nl/~nick Office : Ornstein lab. 172 ---------------------------------------------------------------------- tel. +41-22-7679751 (direct) CERN PPE Division / ALICE exp. tel. +41-22-7675857 (secr.) CH-1211 Geneva 23 fax. +41-22-7679480 Switzerland CERN beep : 13+7294 Office : B 160 1-012 *----------------------------------------------------------------------*

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