Re: [ROOT] Fitting

From: Rene Brun (Rene.Brun@cern.ch)
Date: Wed Feb 13 2002 - 17:03:41 MET


Hi Chris,

In the ROOT fitting functions, two algorithms are currently implemented
  - normal Chisquare method (default)
  - likelihood fit (option "L")

With the likelihood fit, all bins are taken into account.
With the chisquare method, there are two cases:
 - default. Only bins with a non-null error are taken into account.
   In general, this means that all empty bins are ignored. However, you may
   have an empty bin, but have set its error to a non null value. Vice-versa,
   you may have a non-empty bin and set its error to 0.
 - option "W" is specified. In this case all bins are used and all have
   the same weight=1.

Rene Brun

Chris Theis wrote:
> 
> Hi Rooters,
> 
> I've been trying to figure out how the ROOT fitting routines actually
> treat possible empty bins within a histogram. Unfortunately I've not been
> able to find out if they are discarded or taken into account, respectively
> if there is a switch to set the behavior.
> 
> Probably one of you knows anything about this topic. Any hints would be
> appreciated!
> 
> Regards
> Chris
> 
> ---------------------------------------------------------------------------
> Chris Theis
> CERN/EP - European Organisation for Nuclear Research
> 1211 Geneva 23, Switzerland
> Phone: +41 22 767 6592                    Office: 40-2B-24
> e-mail: Christian.Theis@cern.ch           www: http://www.cern.ch/ctheis
> --------------------------------------------------------------------------



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