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gintea
3 Posts |
 Posted - 03/30/2015 : 09:45:19 AM
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Origin Ver. and Service Release (Select Help-->About Origin): OriginPro 8 ver 8.0951
Operating System: Windows 8
Hello,
I have a x,y data set to which I'd like to fit a function y=A*x*ln(x). How do I do that? I tried using Fitting Function Organiser, but I have no idea what Parameter settings and Parameter Initialization to use. Besides, what I need is such a simple function, surely there's an easier way to do this?
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snowli
USA
1379 Posts |
Posted - 03/30/2015 : 12:06:48 PM
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Hello,
In later versions, we have a simpler tool, Fitting Function Builder to guide you step by step to build your fitting functions.
http://www.originlab.com/doc/Origin-Help/UserDef-FitFunc
When defining functions in Fitting Function Organizer, Parameter Settings and Parameter Initialization fields are optional. If you don't set them when defining the function, just make sure when you use Nonlinear Curve Fit dialog to fit with the defined function, first go to Parameters tab to specify some initial value. Otherwise fill can't start.
To avoid specify initial values everytime in Nonlinear Curve Fit dialog, when defining the function in Fitting Function Organizer, you can set
InitialValues = 1(V)
in Parameter Settings field.
it will specify 1 as initial A value. (V) means the parameter values can vary during fitting. If u want it to be fixed, use (F)
If you have multiple parameters, then when defining initial values, use the following syntax
InitialValues = 1(V), 2.5(F)
it will set 1st parameters's initial value as 1, second parameters's initial value as 2.5 and will not vary during fitting since it's set to be Fixed.
Thanks, Snow
OriginLab Corp. |
Edited by - snowli on 03/30/2015 12:10:40 PM |
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How to fit a custom function?