Nonlinear Curve Fitting


ORG-9545Incorrect Standard Error for Parameters of Voigt Fitting FunctionWhen x is large, it can produce a big standard error for xc. Voigt uses numeric derivative, and improper step size can cause a big standard error. In 9.1, it changes the step size to avoid this problem. 

None Ordered Growth/Decay Constants When Fitted With Exponential Functions

In 9.1 when fit multiple processes with exponential growth or decay functions, growth or decay constants will be sorted accordingly. For example in ExpDec 3 function, fitted parameters will be ordered as t1<t2<t3. 

ORG-8878Message TabPreviously, NLFitting dialog always switches to message tab. In 9.1, it always stays at current tab, only switches to message tab when reporting critical errors. 


Customized NLFit dialog and want to see fitted curve when doing fit 1 iteration at a time

1. Run the following code to plot a scatter graph
fname$=system.path.program$ + "Samples\Curve Fitting\gaussian.dat"; // prepare data
plotxy (1,2);

2. Run the following script, and we could curve fit and got the result.
nlbegin 1 gauss tt;
nlpara 1;
nlend 1;

--> NLFit dialog opens with nlpara 1 command.

3. Click “ 1Iteration” button or Fit till converged,
--> Parameter values update on Parameter tab.
==> But the fitted curve doesn’t change in graph. We want that the fit curve in the graph changes when parameters are updated in the dialog.


Fit Comparison


Missing Value Altering Results of Fit:Comparison Dataset

In 9.1, missing value in the end of x column won't affect the result of Fitting Comparison. Incorrect result existed in SR1 and later version of 9.0. 


Analysis Report Sheet


Expand/Collapse on Report Sheet Not Act on Individual Table

Previously, when right click to select expand/collapse on report sheet, it would act on all the tables. In 9.1, it's fixed to act on individual table as selected. 


Repeat Analysis Related

Repeat Analysis Failed to Fix Fixed Parameters9.1 is able to remember fixed parameters settings. Besides, repeat analysis can remember customized data range. 
(ORG-7878)Repeat Analysis to All Y Columns Not Keep Weighting Method9.1 is able to copy weigh method when repeat analysis