Path: news.mathworks.com!not-for-mail
From: "Marcio " <marciobarbalho@yahoo.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: simple parameter estimation
Date: Fri, 10 Oct 2008 15:20:04 +0000 (UTC)
Organization: UFRN
Lines: 24
Message-ID: <gcnrr4$gf1$1@fred.mathworks.com>
References: <gcmgn2$amq$1@fred.mathworks.com> <8782248.1223634898604.JavaMail.jakarta@nitrogen.mathforum.org>
Reply-To: "Marcio " <marciobarbalho@yahoo.com>
NNTP-Posting-Host: webapp-03-blr.mathworks.com
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 8bit
X-Trace: fred.mathworks.com 1223652004 16865 172.30.248.38 (10 Oct 2008 15:20:04 GMT)
X-Complaints-To: news@mathworks.com
NNTP-Posting-Date: Fri, 10 Oct 2008 15:20:04 +0000 (UTC)
X-Newsreader: MATLAB Central Newsreader 1123483
Xref: news.mathworks.com comp.soft-sys.matlab:494574


Torsten Hennig <Torsten.Hennig@umsicht.fhg.de> wrote in message 
> Now in your case an analytical solution for the 
> above system of differential equations 
> seems hard to determine.
> 
> For this reason, you have to couple ODE45 and one of the
> parameter estimation routines:
> 
> In each step k, you get suggestions for parameters 
> a_k, b_k, c_k from lsqnonlin or lsqcurvefit.
> With these parameters, you call ODE45 to
> determine the y_i(t_j,a_k,b_k,c_k) and transfer 
> these values to lsqnonlin or lsqcurvefit.
> In the next step, lsqnonlin or lsqcurvefit will 
> transfer new a_(k+1), b_(k+1), c_(k+1).
> You call ODE45 and so on.

Actually the problem I am trying to solve is pretty much harder than that, I guess it's about over 250 equations, I mean, 250 differential equations and 248 algebraic equations, 598 variables (of course), which gives us a differential-algebraic system of equations, which is, in that case, strictly non-linear. 
Of course, I am trying to solve a simple ODE system before starting with a DAE system.

Ok, let me see whether I got your suggestion straight...
You said to solve the system as albebraic and the result feeds the differential system and so on. I think I misunderstood something, will the results from the differential system feed a new algebraic system?

Thanks for commenting!