Modify Equations In The SigmaPlot  Fit Library


One method for creating a custom curve fitting library is to modify examples from the SigmaPlot Fit Library.

This makes creating the automatic initial parameter estimation equations easier. To do this use the Add Equation to Notebook feature to fill the notebook with your custom equations. Then delete the worksheet and graph and save the notebook as a regression library. Place some data that is typical for the specific application into the worksheet and create a scatter graph.

Find an equation in the SigmaPlot Fit Library that is similar to the one you are entering. For example, for the Peppas equation F = ktn use the 2 Parameter equation in the Power Equation Category y = axb. Click Edit Code and Add As to ‘unlock’ the curve fitting statements and add the new curve fit to the User-Defined section.

Modify the equations, variable definitions and add constraints, if necessary. Modify the automatic parameter estimation equations (or use numerical starting parameter values). For the Peppas equation no changes to the automatic parameter estimation equations are required. Click Next repeatedly through the Regression Wizard and check the Add Equation to Notebook box. Then click Finish.

Make sure that the curve fitting process worked properly and that the equation was added to your notebook. Repeat these steps to add other equations to the library. When you are finished adding equations to your notebook delete the graph and the data worksheet from the section.

You should now have a notebook with one section containing regression icons for each equation you added. Right click on the regression icons and use Edit Info to label them with each equation name. Save the notebook as a SigmaPlot Regression Library. This procedure produced the regression library Release.jfl.

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