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66de250

China
24 Posts
Posted - 10/28/2024 :  1:07:12 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Dear Sirs,I need some assistance with a LabTalk script for nonlinear curve fitting.Below is my specific problem:
First, I have a user-defined function named ‘fuc’, which contains three parameters: "AA", "BB", and "CC". All three parameters have an initial value of '1'. Additionally, I have a dataset and a graph based on this data.
I need to implement the following using a LabTalk script:
Select a specific segment of the data in the graph (e.g., from the maximum value to the last value ) as the fitting range for nonlinear curve fitting.
Use the user-defined function file "fuc" as the fitting function.
Before each fitting, I need to change the initial value of parameter "CC".
Fit until convergence (when I manually operate, I find that may need click the "fit until convergence" button multiple times results in a correct fit, so in the script you need to consider how to ensure the fitting result is correct).
After convergence, I need to extract the fitted parameter "CC" and save it directly into a new worksheet at the i-th row and j-th column.
Could you provide me with a specific LabTalk code to solve this? Thank you very much!

YimingChen

1606 Posts
Posted - 10/28/2024 :  3:00:45 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Please check the following sample script to use the ExpDec1 fitting function to fit the sample data, and save the fitted parameter t1 to a new workbook. You may want to refer to the Labtalk Help page of nonlinear curve fitting:
https://www.originlab.com/doc/LabTalk/guide/Non-linear-Fitting


newbook;
wbook.dc.add("CSV");
wks.dc.source$=System.path.program$+"Samples\Curve Fitting\Gaussian.dat";
wks.dc.import();

int istart = list(max(Col(B)), Col(B)); // get the index of max y value
nlbegin iy:=(1,2)[istart:end] func:=ExpDec1 nltree:=ParamTree;
ParamTree.t1 = 5;
nlfit;

newbook;
Cell(1,1) = ParamTree.t1;


James
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