Re: H1->Reset() in 2D case

From: Rene Brun (Rene.Brun@cern.ch)
Date: Tue Oct 12 1999 - 22:16:46 MEST


Hi Anton,
I cannot reproduce your problem 25 and 26.
Concerning 27 -> 30, I think I understand what could be the problem.
When calling hist->Draw(), a scatter plot is produced.
A number of points is generated ramndomly in each cell proportionally
to the cell contents.
I do not know if you see one dot only or many.
Could you provide a simple macro with a small file to test
your problems?

Rene Brun

On Tue, 12 Oct 1999 KOSU_FOKIN@garbo.lucas.lu.se wrote:

> Hello again,
> 
> I found a strange feature while drawing 2D histograms :
> 
> root [23] chain->Draw("f1e:f1de","","",10000);
> root [24] chain->Draw("f1e:f1de","","",10);   
> root [25] chain->Draw("f1e:f1de>>hist","","",10000);
> root [26] chain->Draw("f1e:f1de>>hist","","",10);   
> 
> Lines [25] and [26] produce identical pictures where (visible) number of dots is the
> same for both figures, while Nent = 10 and 10000 in these two cases (also displayed
> in statistic box).
> 
> Lines [23] and [24] work fine showing different number of scattered dots (as expected).
> 
> Also I get into the same troubles if I call hist->Reset() for a 2D. 
> It resets statistics but if I call 
> 
> root [27] hist->Draw() 
> root [28] hist->Reset() 
> root [29] hist->Draw()
> root [30] hist->Fill(10,10)
> (Int_t)43
> root [31] hist->Draw()
> 
> [27] displays a number of scattered dots, [29] displays a blank histogram, 
> but [31] displays a number of dots ([27]) again. It looks like cells are not set to 
> zero ...
> 
> Did I miss something?
> 
> This runs under root 2.21. Sorry, it's not updated to 2.22 by our sysadmin yet but I
> have not seen any reference to this feature in 2.22 development notes.
> 
> Best regards,
> Anton 
> 



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