Re: [ROOT] Display problem with TProfile

From: Rene Brun (Rene.Brun@cern.ch)
Date: Mon Jun 23 2003 - 08:29:00 MEST


Hi Daniel,

In some cases (like yours), TProfile::GetBinError resets the bin error
to the average bin error in the profile. This happens with some
combinations of small statistics or ratio error/bin_content.
I have disabled this default action in the new version in CVS and added
a new static function TProfile::Approximation to enable it on demand.
see: http://root.cern.ch/root/htmldoc/TProfile.html#TProfile:Approximate

Rene Brun


Daniel CUSSOL wrote:
> 
> Hello rooters,
> 
>  I would like to show you a small problem when a TProfile is displayed.
> In the joint ProfTest.root file, there is a TProfile named "prof" which
> was
> filled with very small Y values (typically around and below 1.e-4).
> When I plot it without scaling, I get uniform error bars which have
> no correlations with the real error bars. When I scale it with the
> command
> prof->Scale(100.) and draw it, the errors bars are correctly displayed
> for the small X values, but incorrectly diplsyed for high X values. When
> I apply an  additional scaling via tp->Scale(10) (the original spectrum
> is now scale by a factor 1000) and draw it, the error bars are correctly
> displayed. It is as if a threshold on error values was set for the error
> bars display. Is this "normal"? Could it be eventually corrected?
> 
>  Thanks for your help
> 
> Cheers
> --
> 
> Daniel CUSSOL
> 
> LPC Caen
> 
> Boulevard du Marechal Juin
> 
> 14050 CAEN CEDEX
> 
> e-mail : cussol@in2p3.fr
> 
> Tel    : +33-(0)2-31-45-29-73
> 
> FAX    : +33-(0)2-31-45-25-49
> 
>   --------------------------------------------------------------------------------
>                     Name: ProfTest.root
>    ProfTest.root    Type: unspecified type (application/octet-stream)
>                 Encoding: base64



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