Path: news.mathworks.com!not-for-mail
From: <HIDDEN>
Newsgroups: comp.soft-sys.matlab
Subject: Re: Double exponential decay fit
Date: Wed, 14 Jan 2009 18:10:04 +0000 (UTC)
Organization: Nortel
Lines: 18
Message-ID: <gkl9ps$rd2$1@fred.mathworks.com>
References: <gkl7vl$nb0$1@fred.mathworks.com>
Reply-To: <HIDDEN>
NNTP-Posting-Host: webapp-05-blr.mathworks.com
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 8bit
X-Trace: fred.mathworks.com 1231956604 28066 172.30.248.35 (14 Jan 2009 18:10:04 GMT)
X-Complaints-To: news@mathworks.com
NNTP-Posting-Date: Wed, 14 Jan 2009 18:10:04 +0000 (UTC)
X-Newsreader: MATLAB Central Newsreader 1176611
Xref: news.mathworks.com comp.soft-sys.matlab:511533


"Jean-Sebastien" <newsreader@mathworks.com> wrote in message <gkl7vl$nb0$1@fred.mathworks.com>...
> Hi folks,
> OK :
> You have a set of data points (time,response) which correspond to a simple two exponential decay function (peak to baseline). 
> You feed sigmaplot10 with it and using the simple equation y=a*exp(-bx)+c*exp(-dx) it gives you a nice fit. 
> Now you do it in Matlab using the same data, same equation and on 2 out of 3 fit you've got a funny fit which obviously is wrong... 
> Question:
> Does anyone can explain the decrepancy between the two softwares? why sigmaplot10 can fit a simple two exponential decay function while Matlab doesn't?
> Is there any issue with the method used? If so is there an alternative to make Matlab fit this simple two eponential decay function correctly?
> Thanks for your help,
> JS
> 

um it's hard to answer your question as you have not really given much information.  It's like me asking why C++ can give me answer but pearl can't.  Matlab is a programing language.  What algorithm are you using to fit the points, in matlab.  What is sigmaplot10?  

My guess is that the algorithm you are using in matlab is messed up slightly.  You shouldn't blame the language for code written in it.

Aaron