15.3.10 Fit Status Code in NLFit Fit Result

In your fit report, you can see a Fit Status Code in the Fit Status field in the Statistics table.

NLFit Error Code-1.png

Please refer to the below table to see what the code means and our suggestions.

Fit Status Code Message Suggestion

-103

Parameters contains missing values.

Try to modify the parameters to proper values.

-101

Invalid parameter value occurred during the fitting.

Check the parameter values.

-100

The fitting session failed.

-1

No iteration is performed.

0

Fitting was aborted by user (Press Ctrl+C to abort the session).

You have just aborted the fit. Want to try again?

1

Chi-square was reduced, but the tolerance was not reached.

Try increasing the number of iterations or change the tolerance value. This can be done from the Iterations branch of the Fit Control node on the Settings: Advanced page.

100

Fit succeeded. Chi-square was reduced and the tolerance was reached.

101

Fit succeeded. Fit converged and Chi-square no longer changed.

Fit converged because Chi-square no longer changed. However, the Chi-square may be large due to an improper model.

102

Fit may have converged, the number of parameters is greater than or equal to the number of input data and results are unreliable.

Either increase the data points in input data, or fix some parameters to reduce number of parameters to be fitted.

-200

Fit did not converge, and the maximum number of iterations has been exceeded.

Your model may be difficult to fit. Try increasing the number of iterations or change the tolerance value. This can be done from the Iterations branch of the Fit Control node on the Settings: Advanced page.

-201

Fit did not converge because of poor data or parameter initialization.

The initial values are too far away from the real ones. Try to find some empirical values from papers or simulate a curve to estimate the initial value (Analysis: Fitting: Simulate Curve). You may need to re-define the function because the model does not seem to match the data.

-202

Fit may have converged, because it cannot find direction to change parameters to reduce Chi-square.

This could be caused by "too perfect" initial values or over-parameterized/improper model. Try to adjust the initial values or fix one or two parameters.

-203

Fit did not converge, because mutual dependency exists between parameters.

The model is over-parameterized, so the fitter cannot find a fixed parameter value. Try simplifying the function, or fixing several parameter values.

-204

-205

-206

Fit did not converge, because error/weight values are not compatible with the chosen weighting method.

-207

Fit did not converge, for some other unknown reason(s).

The reason could be improper initial values and parameter constraints or wrong model, etc.

-1000

Fit did not complete - partial iterations were performed.

Reopen the NLFit dialog and click the Fit until Converage button.