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Re: Re: NonlinearRegress of user functions

Dear Jean-Marc, Dear All,
You are right that parameter A, B, C, D, E should be lowercase or longer name. In order to shorten long parameters for the discussion, I write 5 parameters in single capital letter, A, B, C, D, E. In practice the parameters is longer and module psT[Texp,pA, pB, pC, pD, pE]  and rhocal = rhoT[Texp, pA, pB, pC, pD, pE] run perfectly. 
The problem for me is that I can not find out correct 5 parameters by using NonlinearRegress or NMinimize to fit the experimental data. May be I need to use other commands or modify my syntax or procedure or manipulation... to solve the problem.
I would appreciate if you or anyone can help me to solve the problem.
Thanks and regards,

 Lai Ngoc Anh

----- Original Message ----
From: Jean-Marc Gulliet <jeanmarc.gulliet at>
To: mathgroup at
Sent: Monday, August 25, 2008 11:57:04 AM
Subject: [mg91558] [mg91534] Re: NonlinearRegress of user functions

Ngoc Anh Lai wrote:

> I have experimental data set of (Texp, pexp, rhoexp). With each value of
> Texp, I will calculate pcal and rhocal by using functions pcal = psT[T,
> A, B, C, D, E]  and rhocal = rhoT[T, A, B, C, D, E]. Parameters A, B, C,
> D, E of the functions psT and rhoT will be found by Minimization of 


FWIW, though I cannot tell for sure whether this is the source of your 
problems, note that, in general, it is a very bad idea to use single 
capital letters as names of variables because many of them have already 
been attributed some predefined meanings (every Mathematica built-in 
command begins with a capital letter). For instance, D is the 
differential operator, E is the base for natural logarithms. You should 
use longer names and/or start them with lowercase letters.

-- Jean-Marc

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