Set parameter limits or set constraint?

Hello folks,

Suppose I am fitting a histogrma by a function of three variables: A, B, C. Setting limits on one one parameters is quite simple: using SetParLimits.

I need to know how to do it for a combination of these paramters, i.e. set a constraint. For example set the parameter limit on “A*B”.

I can do some coding trick, but I am not sure if we can do it with root facilities.



This can be implemented in a straight-forward way using Lagrangian
multipliers and Minuit . It is spelled out step-by-step in the last part


This will be implemented in the future as a standard option in Minuit .