Re: Drawing vars from a TTree

From: Rene Brun (Rene.Brun@cern.ch)
Date: Thu Jun 26 1997 - 11:20:46 MEST


Nick van Eijndhoven wrote:
> 
> Dear ROOTers,
> I have all my physics column wise ntuples now converted into root
> files (i.e. trees) and would like to do the following :
> 
> * Draw variable A versus B with a weight W under the condition that C>D
> 
> In PAW I can do this by :
> 
> nt/plot 999.A%B W*(C.gt.D)
> 
> and in ROOT I tried :
> 
> Root> TChain q("h999")
> Root> q.Add("test.root")
> Root> q.Draw("A:B","W*(C>D)")
> 
> but when I inspected the produced 2-dim histo in Lego layout all
> heights were at 0.
> 
> Question : How to achieve this in ROOT ?

By default the command:
   q.Draw("A:B",...) 
produces only a scatter plot.
If you want to look at the result as a lego plot, you should save
the result in a 2-d histogram.
   q.Draw("A:B>>h2","W*(C>D")
will create a TH2F object named h2. You can draw h2 with all
supported options.

Rene Brun



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