Problem in fitting: Abnormal termination of minimization

Roofit and RooStats
1

Dear all,

I am trying to fit some points (please find that attached)
with a function of type: p0 + p1/x^{p2}

It is giving me warning:

Warning in <Fit>: Abnormal termination of minimization. FCN=0.36281 FROM MIGRAD STATUS=CALL LIMIT 1345 CALLS 1346 TOTAL EDM=0.00011369 STRATEGY= 1 ERROR MATRIX UNCERTAINTY 26.5 per cent EXT PARAMETER APPROXIMATE STEP FIRST NO. NAME VALUE ERROR SIZE DERIVATIVE 1 Const 2.34916e-01 1.93354e-02 1.59776e-04 -7.12223e-01 2 b 6.79464e+08 2.99201e+09 3.09998e+07 -1.50918e-10 3 power 6.28887e+00 1.29026e+00 1.39157e-02 3.45751e-01

But it fits the points.
Then I try to get the confidence intervals from this fit by doing:
(TVirtualFitter::GetFitter())->GetConfidenceIntervals(n);

and then it gives me (in addition to above warnings):

Error in <TBackCompFitter::GetConfidenceIntervals>: Cannot compute confidence intervals with an invalide fit result

What would you suggest in this case?

Thanks,

Best Regards,
Shilpi

plot_fakerateVspT_25nov.gif596×572 8.08 KB

2

Hi,

The minimization exceeded the number of calls. You can try to extend by setting to a larger value (e.g. 10000).

ROOT::Math::MinimizerOptions::SetDefaultMaxFunctionCalls(10000);

Also you could try to increase the tolerance for convergence:

ROOT::Math::MinimizerOptions::SetDefaultTolerance(1);

Lorenzo

3

Hello Lorenzo,

Many thanks.

worked for me.

Best Regards,
Shilpi