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problem with nonlinear fit

• To: mathgroup at smc.vnet.net
• Subject: [mg25477] problem with nonlinear fit
• From: "Dragan Grgic" <Dragan.Grgic at ensg.inpl-nancy.fr>
• Date: Mon, 2 Oct 2000 22:26:56 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

Hi everybody,

I have to fit the function e = (s/K)^(Na)*(t/a)^a    (s = constant; 
t = variable; K,N,a = parameters) to a given set of datas.
Then, I have used the NonlinearFit function (Statistics'NonlinearFit' 
package), but I have two problems:

1) I can't specify any start values or range using. I tried to give them
as any forms, but I always got error messages concerning these 
parameters.

2) mathematica shows kind of a strange behavior when repeating the fit 
operation, sometimes it keeps old values and sometimes it reports 
different error messages.


Any help welcome,
Thanks in advance, Dragan.