TH1::FIT (Fitting a user defined function)

ROOT
#1

Hi.

based on the myfit.C tutorial, in order to fit an “experimental” histogram to a pretty complicated model (12 parameters), i have written the attached code.

the fit function, pBSim, needs the objects and variables which are defined between the “<<< START HERE” and the “<<< STOP HERE” comment lines. However, these definitions are needlessly performed each and every time the function is called. Basically, they can be defined in the void pBfit() function, but then i pBSim couldn’t access them…
Im not only new to ROOT but also to C++. :blush:

My Question Is: how do i make these definitions outside the function so that the objects will “live” also in the scope of the function? (or any other idea is welcome).

Thanks in advance, :slight_smile:
Moshe (PSI, Switzerland)
pBfit.C (2.49 KB)

#2

I do not understand what you try to do with your pBsim function and Graphmuonprofile. Anyway, you can recode your example as shown in the attachement

Rene
pBfit.C (2.57 KB)

#3

pBsim is the probability that (in a muSR experiment) the muon will stop in the sample at a field B.

Graphmuonprofile is just the implantation profile of the muons in the sample (low energy muons).

your code is indeed the programmatic solution to the problem. i forgot that one can declare variables and classes for “future use”. However, since pBsim has statistical nature (it is a simulation), minunit won’t converge. i have since tried a different approach and it worked.

Thanks a lot.