Dear experts,
I would like to understand what is exactly
“estimated distance to minimum” and how it is calculated.
Second questions is the following:
I run unbinned fit and see in my printout lines lines like
Info in : VariableMetricBuilder 3 - FCN = -0.002022590529 Edm = 0.0009089154139 NCalls = 958
after some iterations fit is converged and print me best fit parameters after the line
Info in : VariableMetricBuilder 6 - FCN = -0.003814485944 Edm = 7.009636942e-05 NCalls = 1758
The after parameters printout I have this following
RooFitResult: minimized FCN value: -0.00381449, estimated distance to minimum: 0.000176492
covariance matrix quality: Full, accurate covariance matrix
Status : MINIMIZE=0 HESSE=0
so, there is a difference between “estimated distance to minimum: 0.000176492” and “Edm = 7.009636942e-05…” Why it is so ?
Question 3. Sometime, very rare I have very large value of Edm (for example 50) and unphysical result of fit : Delta NLL is very large which can’t be in my case. Is it due to fit can’t find a good minimum ?
Thank you, Sasha.