How to make fit with log-likelihood method using TGraphErrors

[Wile_E_Coyote]

It seems to me that you need to write your own “likelihood function”, and then you can use the "U" graph fit option, or maybe better:

Minimization in PyROOT

Hi, The recommended way to minimise a function is to use the ROOT.Math.Minimizer class. There is this tutorial, ROOT: tutorials/fit/NumericalMinimization.C File Reference, but it is in C++. If you have issues translating it in Python, please let me know, I can provide that example also in Python Lorenzo