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tlawren
USA
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 Posted - 05/12/2008 : 09:41:09 AM
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Origin Version (Select Help-->About Origin): 7.0 sr1
Operating System: XP sp3
I apologize if this is a repeat question. I searched for similar questions, but the search timed out every time.
I am trying to do a simple non-linear fit, namely an elastic curve. I have gone though the nl-fit tutorial and everything worked fine, but when I try my own function I continually get errors. I have been creating a user defined function
y=0.5*s*x^2
so 's' is the only parameter. My datasets are assigned properly and I have initialized my parameter appropriately. When I try to run iterations, I get
Error 28037. Likely caused by errors in user defined formula or poor parameter initialization.
I can initialize the parameter to a value I know it should be and I get the error and no output. What might I be doing wrong? Are there any better tutorials for fitting? |
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greg
USA
1378 Posts |
Posted - 05/14/2008 : 1:06:58 PM
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Most likely reason is that you saved the function in Expression form, whereas you defined it in script Form.
Delete the "y=" from the definition and re-save, other change the Form to Y-Script and re-save.
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pdn
1 Posts |
Posted - 08/13/2008 : 10:02:37 AM
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Version: OriginPro 7.5 SR6 v7.5885 (B885)
I'm experiencing a similar problem when trying to perform a fit with a user defined function, but since I'm using a different version, I'm not sure whether the solution is the same - I can't seem to choose between different formats for saving formulas.
In addition I've noticed that when going into the "fitting session" window, the buttons for "100 iterations" and "100 simple iter." say some big number, as shown in the screen shot below.
I've previously fitted successfully using the same data, function and initial values.
The first time experienced the problem was when trying to fit 43 curves simultaneously, and solved the problem by reducing the no. of fits to 20, but now I can't even perform a single fit.
I have tried to restart the computer. |
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Deanna
China
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Posted - 08/14/2008 : 9:44:34 PM
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Hi,
From the screenshot, we did see a large number in the n Itera(tions) Button. The n value from the Max. Number of Iterations drop-down list in the Control Parameters dialog box. Would you please check this drop-down list to see whether a large value is selected?
In addition, equation form can be selected in the Form drop-down list after you have selected Function: Edit from the menu of the Non-Linear Curve Fitting dialog and then cleared the Use Origin C check box. But, this does not seem to be related to the problem.
Deanna
OriginLab Technical Services |
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newkiwi
2 Posts |
Posted - 09/22/2008 : 12:56:08 PM
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Hello,
I use Origin 7G and Windows XP.
I tried to fit some complex data and suddenly the number of Iterations was increased to some strange value. Afterwards I was not able to fit any curve with a self-defined function.
Not even y = ax+b was possible.
I always get "Error 28037. Likely caused by errors in user defined formula or poor parameter initialization"
It's definetly not a problem of the function since easy functions don't work as well and it is not a problem that the starting values are too far off. I take the same functions as before the problem and it does not work.
Thanks for your help
Christian
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fitting problem