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liam12345
2 Posts |
 Posted - 12/18/2014 : 9:10:15 PM
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Origin Ver. and Service Release (Select Help-->About Origin): 9.1.0
Operating System: Win8 (Parallels)
Hello!
I'm trying to use OriginPro9.1 for curve fitting. My model has a single independent variable (x), two dependent variables (y1, y2), and 10 shared parameters (v1, v2,...) to be fitted. I defined my function using the Function Builder:
-->Explicit
-->Equations
y1 = f(x, v1,v2,...)
y2 = f(x, v1,v2,...)
The "quick check" feature returns the correct values at all x
Here's the problem: When I attempt to fit my experimental data, only x-values at which both y1 and y2 have a defined value are included during the fit. As such, the fit excludes a large portion of the y2 values (which are experimentally assessable long after the y1). To get the correct parameters, the FULL set of data must be fitted simultaneously.
I have tried any number of ways to select my data in the appropriate way, but nothing seems to work.
Any help is greatly appreciated!
Li
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JacquelineHe
287 Posts |
Posted - 12/19/2014 : 04:49:12 AM
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Hi,
I suggest you can set you dataset to X1Y1X2Y2, and try to use Global Fit.
If you use the same function for y1 and y2, you can use global fitting with parameter sharing. Please refer to this help page:
http://www.originlab.com/doc/Tutorials/Fitting-Global
If you use the different function for y1 and y2, you can use global fit for different dunctions with shared parameters.
1. When create functions, set independent variable:x, dependent variables:y, parameters:v1, v2,... and add parameters "s"
2. Type the expression which contained formula of function(1) and function(2) in the function body box:
s*function(1)-(s-1)*function(2)
The parameter s is a switch for global fitting, if s=1, the function(1) is used for fitting, if s=0, function(2) is used for fitting. The value of s will be controled in the following fitting procedure
Then, click Finish.
3. In NLFit dialog, go to the Data Selection Page, Select Global Fit mode from the Multi-Data Fit Mode drop-down list.
4. Go to the Parameters tab. Check on the Share check box for the parameters you need to share, and check on the Fixed check box for "s" and "s_2", and set "s" value to 1, "s_2" value to 0.
5.Click the Fit button to fit curves.
And the detail tutorial is sent to you by email. Please check it.
Thanks
Jacqueline
Originlab |
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liam12345
2 Posts |
Posted - 12/19/2014 : 3:14:45 PM
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| Thank you! That fixed my problem. :) |
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Fitting 1 independent and 2 dependent variables