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Error with first order exponential decay

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najones84

1 Posts

Posted - 03/05/2009 : 08:20:49 AM

Origin Ver. and Service Release (Select Help-->About Origin):
Operating System:

Hello,

I was wondering if anyone can help me. I have a small data set of normalised values and the S.E.M, which i'm trying to plot a fitted exponential decay (first order). However, when i go to generate the fit an error message occurs saying "parameters are not properly initialized". This fitting worked fine on a same sized data set a few weeks ago and i just can't get my head around the problem (it's been a few days). I'm quite new to origin with no knowledge computer coding, so if anyone can give me a idiots guide to solve this problem it would be of much help.

Below is the data set i'm trying to plot to get a nice graph, r2 value and the y= A1 *exp (-x/t1) + y0 equation

Time Mean (normalised) SE

40 1 0
70 0.871997487 0.067707257
100 0.781273758 0.088397711
130 0.652044057 0.089901812
160 0.589689689 0.123395865
190 0.589514592 0.149950961

Thanks in advance

Nick

Shirley_GZ

China
Posts

Posted - 03/06/2009 : 02:22:47 AM

Hi Najones84,

In Origin 8.0, the built-in function named as ExpDec1 is exactly waht you want. Use the built-in function, do the Nonliear curve fitting with weight, please see the following pages:

http://www.originlab.com/www/helponline/Origin8/en/origin.htm#Regression_and_Curve_Fitting/Fitting_with_Errors_and_Weighting.htm

http://www.originlab.com/www/helponline/Origin8/en/Tutorial/Tutorial.htm#Tutorial/NLFIT_Built_In.html

Any problem ,please feel free to contact with us.

Best regards,
Shirley

Originlab Technical Service Team

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