Re: Drawing vars from a TTree
Rene Brun (Rene.Brun@cern.ch)
Thu, 26 Jun 1997 11:20:46 +0200
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