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Yan
07/15/12 05:56am

Hello,

this is a problem that's driving me crazy. I have some simple experimental data (about 80 data points) which I want to fit to an exponential curve (a*exp(bx)).

The ListPlot looks fine. It's a relatively "flat" curve, I'm guessing b lies between 10^-3 and 10^-5. I have tried to fit the data with FindFit, NonlinearModelFit. I have even done a linear fit, which works just fine (although of course it's not what I want).
But whenever I try to fit the curve to an exponential function, Mathematica returns b = 1 and that the precision goal was not met. I have tried adjusting the MachinePrecision, PrecisionGoal and WorkingPrecision, all to no avail.

I have attached the data with a ListPlot and two failed fits.
Since I can't wrap my head around it, I'm hoping that you can.

Any help would be appreciated, thanks in advance!
Greetings,
Yan

Attachment: ExpFit.nb, URL: ,

Subject (listing for 'Problem with simple exponential fit')
Author Date Posted
Problem with simple exponential fit Yan 07/15/12 05:56am
Re: Problem with simple exponential fit Bill Simpson 07/16/12 3:38pm
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