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Chillkroete
5 Posts |
 Posted - 01/21/2014 : 5:24:59 PM
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Dear Community,
I guess I have a very simple question, but I am completely new to Origin.
I want to do a simple regression fitting with a bunch of Data points. As exponential fitting function I want to use: A *exp(-B*x)
But after plotting my dataset I cannot find a fitting curve like that. Do I have to create a new fitting curve or did I just overlook the right curve?
Thank you for your support!
Cheers
Chillkroete |
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AmandaLu
439 Posts |
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Chillkroete
5 Posts |
Posted - 01/22/2014 : 6:04:25 PM
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Hi Amanda,
thank you for your reply!
I tried EXP2PMOD1 and I found the correct formula (of course you were right! ;) )
But unfortunately the fitting looks absolutely weired, as you can see here:
On the sceenshoot you only see the fit very light. Its just a line at the X-Axis.
If I use Asymptotic1 for example It looks quite well, but of course It does not have the desired parameter like: A *exp(-B*x)
Do you have an Idea what I did wrong?
Thank you for your help! |
Edited by - Chillkroete on 01/22/2014 6:07:40 PM |
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lkb0221
China
497 Posts |
Posted - 01/23/2014 : 4:48:33 PM
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Hi#65292; Micha
I think you can try ExpDecay1 function (y0 + A1 * exp(-(x-x0)/t1)).
Still not a good fit, but I think it's acceptable.
It is the same as Exp2pMOD1 but with a y offset.
Zheng
OriginLab
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Chillkroete
5 Posts |
Posted - 01/25/2014 : 04:38:50 AM
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Cool, that works quite well for most of my Data, thank you!
But I have one Dataset, which does not look nice:
Do you have an idea what might be the preoblem, why the fit looks weired? Looks like the points in te middle are not considered.
Thank you for your reply! |
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Echo_Chu
China
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Posted - 01/26/2014 : 01:15:26 AM
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Hi, Chillkroete
It looks you did not hit the Fit until converged button when using the ExpDecay1 function. Please look at the fitted curve after I hit the Fit until converge button. However, there is also warning message to remind "you may have overparameterized the fitting function. Fixing one of them may eliminate this problem"
So I also tried fix x0 to 2010 and the fit looks good.
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Chillkroete
5 Posts |
Posted - 01/28/2014 : 10:04:07 AM
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| Allright, now it works perfectly! Thanks a lot at all! |
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Exponential fitting