minimization with correlated parameters

From: Sébastien Gadrat <>
Date: Tue, 15 Feb 2005 18:36:17 +0100

Hi Rooters,

  I am fitting some spectra with a functional which is made in several elementary components (a sum of more simple functions, each of them representing a given contribution to my spectrum). Each elementary function has one and only one free parameter (this parameter can be use to determine the integral of the given component so the number of events which are in it).
  But I would like to constrain some parameters to move only within a given interval, whose bounds are given by another free parameter (but fixed at a given moment of the minimization). I would like my interval to be updated for each new step to take into account previous value returned by the previous step for the free parameter it depends. As an example, I am fitting some J/psi and psi prime spectra and I want that the number of psi prime is let say within 1/30 and 1/70 times the number of J/psi. I know about TF1::SetParLimits but I do not think I can use it in my case since I do not know the magnitude of my different contribution before fitting and my interval will not be updated at all while minimization...
  Is there a way to do that in ROOT ?

Thanks in advance,
Best regards,

Sebastien Received on Tue Feb 15 2005 - 18:36:25 MET

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