4.56 FAQ-768 在非线性拟合中如何得到每次迭代的拟合参数？

Fit-Parameters-Each-Iteration

Last Update: 7/15/2018

您可以使用 LabTalk 函数 Nlbegin 和 Nlfit 来执行非线性拟合，由此获得非线性拟合每次迭代的拟合参数。

// import sample data into a new book
newbook;
fname$=system.path.program$ + "Samples\Curve Fitting\Exponential Growth.dat"; //prepare data
impASC; 
// Start a fitting session;
 
 
nlbegin iy:=2 func:=ExpDec1 nltree:=tt;
getnumber -s (Input the iterations) n;     //Construct a dialog to enable user enter the iteration he want to perform
double aa=0;
 
 
loop (i,1,n)
{
	nlfit $(i);  //run the i-th iteration of fitting

	type "The parameter value in $(i) iteration";  
	 
	type "y0= $(tt.y0, %4.6f)";  //output the parameter values
	type "A1= $(tt.A1, %4.6f)";
	type "t1= $(tt.t1, %4.6f)";

	if (tt.fitstatus == 100)
	{
		type "Fit converged, no more iteration will be done";  
		break;
	}
}
 
nlend;

当您在 Input the iterations 中输入 8 时，即可得到相似的结果：

The parameter value in 1 iteration
y0= -0.162869
A1= 1.283508
t1= -0.998789
The parameter value in 2 iteration
y0= -0.038538
A1= 1.195022
t1= -0.968684
The parameter value in 3 iteration
y0= -0.038365
A1= 1.194898
t1= -0.968641
Fit converged, no more iteration will be done

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Keywords:LabTalk, nonlinear fitting, iteration, fitting parameter, 非线性拟合，迭代，拟合参数