Unlike standard Linear Fitter Tool, also available via IDMApplication2 interface of DM2003 application objects, General Linear Fitter Tool uses external DMFitter control which may be not installed with DM2003. However, this control allows you to perform linear regression with arbitrary basis functions given by user-defined expressions as shown on the screenshot below.

First you should plot data to be fitted since this tool works only with active plot series; then you will be able to start General Linear Fitter HTML application in the Browser window. Your data will be plotted in a new temporary data window.

Define terms of your linear basis (exactly one basis term per line, empty lines are not allowed) or select previously used expression from the dropdown list. Basis terms must be composed from internal functions (see expression syntax for more details), operators and cx parameter (independent variable). Also you may use plot selector tool to restrict fitting data range.

Click "Fit" button to calculate and display parameters and best fit curve. If the model was defined incorrectly, you will see appropriate error message.

When you click OK button, you may save fitting results in several ways. Available options are: copy best fit curve to the new plot series in the source window, add fitting results to the Notes window or add parameter set to the selected worksheet.