Hi Mat, With the L option you use the Poisson distribution to calculate the likelihhod function, default is the Gaussian distribution which results in the minimization of a chi-square. The Poisson Likelihood function has not a problem with a bin contents of zero. see for instance "data analysis" by Siegmund Brandt , page 196, example 7.4 The comment "L" Use Loglikelihood method (default is chisquare method) in the code is confussing because we always use a Loglikelihood method > X-Authentication-Warning: oxpc01.fnal.gov: msmartin owned process doing -bs > Date: Mon, 21 May 2001 11:25:06 -0500 (CDT) > From: Matthew Martin <msmartin@fnal.gov> > To: roottalk@pcroot.cern.ch > cc: Todd Huffman <t.huffman1@physics.ox.ac.uk> > Subject: [ROOT] chisquare > MIME-Version: 1.0 > X-Filter-Version: 1.3 (wren) > > Hi Rene, > When I do something like: > > hist_bp_PtResidWeight->Fit("gaus","L"); > > how is the resulting chisquare defined? Ie how does it deal with the > possibility of some bins with zero events in them? > > cheers > > Mat > Eddy A.J.M. Offermann Renaissance Technologies Corp. Route 25A, East Setauket NY 11733 e-mail: eddy@rentec.com http://www.rentec.com
This archive was generated by hypermail 2b29 : Fri Jun 08 2001 - 11:51:25 MEST