15.3.2.6 NLFit Dialog Buttons

NLFit-Dialog-Button

Buttons Summary

The buttons in the middle portion of the NLFit dialog box provide controls over the fitting process and access to the Fitting Function Organizer. The Organizer is used to edit or define new fitting functions.

	Search and Insert Functions	Click to search an appropriate function and insert it into dialog with Search Fitting Function dialog.
	Edit Fitting Functions	If you have selected a built-in function, this button opens the Fitting Function Organizer. If you have selected a user-defined function, this button opens the Fitting Function Builder.
	Create New Fitting Functions	Click to create a new fitting function with the Fitting Function Builder.
	Save FDF File	Save changes to the current user-defined function. See: Fitting Function Organizer.
	Reorder peaks	Restore default order of peaks. Available only after using Sort Peaks, and when Number of Replicas is more than 0.
	Sort Peaks	Open Sort Peaks dialog. Peaks can be sorted by Centers, Widths, or Amplitudes, in Ascending or Descending order. Available when Number of Replicas is more than 1.
	Initialize Parameters	Initialize the parameters with the parameter initialization code (or supplied values). See:Parameter Initialization.
	Simplex	Perform a Simplex approximation for parameter initialization. See: Downhil Simplex Algorithm
	Calculate Chi-Square	Calculate the current reduced Chi-square value. The result will be displayed in the Message tab of the dialog's lower panel. See: Theory of Nonlinear Curve Fitting.
	1 Iteration	Perform a single Levenberg-Marquardt (LM) iteration. The result will be shown in the Message tab of the lower panel. See: Theory of Nonlinear Curve Fitting.
	Fit until converged	Perform the fit. Levenberg-Marquardt (LM) iteration will be carried out until the tolerance is reached, or the number of iterations has reached the maximum specified in Fit Control branch in the Advanced page of the Settings tab. See: Theory of Nonlinear Curve Fitting.
	Independent Fit Drop-Down list	This drop-down list is only available when performing a multi-data fit in Independent mode. Use it to select the input datasets before selecting 1 Iteration or Fit Until Converged. For more information, see this tutorial.
	Fit	Perform the fit and output the results worksheets. See also: Fit Parameter Values Displayed in Change Parameter Mode.
	Done	Accept the current parameter values, close the NLFit dialog, and generate reports. See also: Fit Parameter Values Displayed in Change Parameter Mode.
	OK	Once clicked, the Fit until converged button becomes an OK button. Click OK to close the dialog. See also: Fit Parameter Values Displayed in Change Parameter Mode.
	Cancel	Cancel the fit and close the dialog.
	Show Top/Bottom Panels	Toggle the top and bottom panels on and off.

Fit Parameter Values Displayed in Change Parameter Mode

When you perform curve fitting with recalculate mode set to Manual or Auto, you can easily reopen the NLFit dialog from an output worksheet or graph. Simply left-click the lock icon on the worksheet or graph, and then click Change Parameters.

The parameter values displayed in the Parameters tab are the same as when the dialog was last closed. As there is more than one way to close the dialog in a fitting session, the displayed values will depend on the actions performed by the user:

• Fit button used
  • If no iterations are performed and the Fit button is used to fit the data and close the dialog, then the displayed values will correspond to the initial values for the parameters.
  • If several iterations are performed, but the fit is not yet converged, and the Fit button is used, Origin will perform the remaining iterations to fit the data and close the dialog. However, in Change Parameters mode, the Parameters tab will display the not-yet-converged values that were present before the Fit button was clicked.
• OK button used
  • When the OK button is present and you click on it to close the dialog, Change Parameters mode will show parameter values as they are listed in the report sheet tables.
• Done button used
  • When the dialog is closed using the Done button, Origin will report fitting results and parameter values without performing any further iterations. This happens regardless of whether the fit has converged. Change Parameters mode will show parameter values at the time the Done button was clicked.