Info about warning during fit

From: Alberto Pulvirenti <alberto.pulvirenti_at_ct.infn.it>
Date: Wed, 26 May 2010 11:33:31 +0200

Dear ROOTers,

I tried to fit a 4-points histogram with a function, and the messages coming out from this were the following:

Warning in <Fit>: Abnormal termination of minimization.   FCN=196.407 FROM MIGRAD STATUS=CALL LIMIT 1354 CALLS 1355 TOTAL

                      EDM=0.119482    STRATEGY= 1  ERROR MATRIX 
UNCERTAINTY  25.4 per cent
   EXT PARAMETER                APPROXIMATE        STEP         FIRST
   NO.   NAME      VALUE            ERROR          SIZE      DERIVATIVE
    1  p0           4.35504e+08   5.93416e+07   1.03921e+07  -1.89308e-07
    2  p1           4.81494e-03   1.32883e-04  -1.25183e-05  -1.00685e+05
    3  p2           6.22473e+00   3.22669e-02   3.13859e-03   2.24320e+02

Warning in <TBackCompFitter::GetCovarianceMatrix>: Invalid fit result Error in <TF1Helper>: Fitter has no covariance matrix Warning in <TBackCompFitter::GetCovarianceMatrix>: Invalid fit result Error in <TF1Helper>: Fitter has no covariance matrix Warning in <TBackCompFitter::GetCovarianceMatrix>: Invalid fit result Error in <TF1Helper>: Fitter has no covariance matrix Warning in <TBackCompFitter::GetCovarianceMatrix>: Invalid fit result Error in <TF1Helper>: Fitter has no covariance matrix Warning in <TBackCompFitter::GetCovarianceMatrix>: Invalid fit result Error in <TF1Helper>: Fitter has no covariance matrix

The last errors were due probably to my attempt to compute the integral error, which probably fails due to this "abnormal termination" of the fit. How can I check what's wrong with the fit and how I can get rid of that?

Thanks, cheers

        Alberto Received on Wed May 26 2010 - 11:33:37 CEST