I’m attempting use the Math::Minimizer interface to Minuit2 Migrad. I’ve ported this code from TFitterMinuit on the advice of experts on RootTalk, and was able to access the covariance matrix before.
It seems that calls to Minimizer::CovMatrix or Minimizer::Correlation always return zero. This is true for fits that converged (status 0) and fits that failed.
I’m using root version 5.22/00d. Does anyone have any suggestions on how to debug this problem?