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hjskofficial
10 Posts |
 Posted - 10/16/2023 : 03:42:27 AM
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Origin Ver. and Service Release (Select Help-->About Origin): Origin 2018
Operating System: Windows 10
Hello everyone,
I defined a Fano function for fitting a curve recently. The function is written as y=y0+H*(1+(x-xc)/(q*w))^2/(1+((x-xc)/w)^2), where y0 is offset; H is amplitude; xc is x center; q is a Fano parameter; w is x width.
While I fitted a curve, the Origin always said "Fit did not converge - mutual dependency exists between parameters. You may have overparameterized the fitting function. Fixing one of them may eliminate this problem." However, no matter I fixed any of the five parameters mentioned above, the same message was always shown.
Does anybody know how to solve the problem?
Thank you very much.
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YimingChen
1613 Posts |
Posted - 10/16/2023 : 09:28:20 AM
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After you fix the parameters, do you still see strong dependencies between fitting parameters in the parameters table in the NLFit dialog?
Could you share your data here for us to test? Thanks.
James
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hjskofficial
10 Posts |
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YimingChen
1613 Posts |
Posted - 10/16/2023 : 1:48:59 PM
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Please set the initial values of the parameters to be close to the values shown below.
James |
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hjskofficial
10 Posts |
Posted - 10/16/2023 : 10:25:53 PM
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Hi James,
Thank you very much for your kind instruction.
Are the initial values universal for all the curve fitting by Fano function? How to choose appropriate initial values?
Sincerely,
HJS
quote:
Originally posted by YimingChen
Please set the initial values of the parameters to be close to the values shown below.
James
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YimingChen
1613 Posts |
Posted - 10/17/2023 : 11:15:36 AM
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Please check the figure below on initializing the parameters in the Fitting Function Builder dialog.
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hjskofficial
10 Posts |
Posted - 10/20/2023 : 04:54:08 AM
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Hi James,
Thank you very much for your kind reply. All the Fano-like curves are fitted successfully.
Sincerely,
HJS
quote:
Originally posted by YimingChen
Please check the figure below on initializing the parameters in the Fitting Function Builder dialog.
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aplotnikov
Germany
165 Posts |
Posted - 10/20/2023 : 09:08:05 AM
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Seems, that LaTeX support may be helpful on the forum. |
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Topic |
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A problem of user-defined function fitting