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lsjuniii
2 Posts |
 Posted - 02/07/2018 : 07:23:46 AM
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Origin Ver. 2018 and Service Release (Select Help-->About Origin):
Operating System: Windows 8
Hi,
I am a beginner in Origin and try to make my fitting with some data.
However, there are many built-in function in linear/nonlinear model.
But I cannot find any reference or detail for the built-in fuctions in Origin.
Does anyone knows about the detailed reference on "Allometric2" one of function in the category of nonlinear/power model?
(Unfortunately, I got the different values with the built-in function as shown in the attachment. I guessed the function should be used in very limited case or conditions.)
It seems to be similar result using built-in and user definition.
But this is very different exponent, the meaning of physical situation.
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Edited by - lsjuniii on 02/07/2018 07:32:17 AM |
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arstern
USA
237 Posts |
Posted - 02/07/2018 : 09:42:10 AM
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Hi,
We have documentation online that provides the equation for each fitting function, the parameters, and a sample curve to help show how the defined equation is applied.
https://www.originlab.com/doc/Origin-Help/Allometric2-FitFunc
You can as well see this in the nonlinear fit dialog. With the dialog open, once you select the defined fitting option in Category and Function.
1. Select the Formula Tab which will display the formula used for that fitting function.
2. Select The Sample Curve which will show what type of curve the fitting function will make and how the parameters are defined.
Here is a link to the documentation for Nonlinear Curve Fitting. Such as, Theory of Nonlinear Curve Fitting, how to set up Parameters and Constraints, and Fit Comparisons.
https://www.originlab.com/doc/Origin-Help/Nonlinear-Curve-Fit |
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lsjuniii
2 Posts |
Posted - 02/07/2018 : 7:08:24 PM
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Hi, arstern.
I knew the page of simple documentation but this was not what I wanted.
You did not explain why there is a different result between two trials.
I cannot find any information on the originality of the function.
Some users used a implemented function on Origin without any care.
Maybe, this can lead to the different result.
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Edited by - lsjuniii on 02/07/2018 7:09:54 PM |
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arstern
USA
237 Posts |
Posted - 02/08/2018 : 09:49:57 AM
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Hi,
Are the parameters exactly the same for Allometric 2 fit and power_user?
When you select fit, the dialog will perform multiple iterations until it makes an approximate guess. Which means the parameters may be different unless you set them to fixed. There could be other settings that are set differently?
If you would like you can send your project file and user defined .fdf file to tech@originlab.com, therefore I can test with your dataset by fitting with Allometric2 and your user defined fitting function. The .fdf file will be located here: \Documents\OriginLab\User Files\fitfunc
Thanks
Aviel
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Reference of preloaded functions in Origion.