Equation Editor (simulation)

The Equation Editor allows you to create or modify a custom equation for your predictive model.

  • The expression for the equation can contain fields from the active dataset or new input fields that you define in the Equation Editor.
  • You can specify properties of the target such as its measurement level, value labels and whether output is generated for the target.
  • You can use targets from previously defined equations as inputs to the current equation, allowing you to create coupled equations.
  • You can attach a descriptive comment to the equation. Comments are displayed along with the equation on the Model tab.
  1. Enter the name of the target. Optionally, click Edit under the Target text box to open the Defined Inputs dialog, allowing you to change the default properties of the target.
  2. To build an expression, either paste components into the Numeric Expression field or type directly in the Numeric Expression field.
  • You can build your expression using fields from the active dataset or you can define new inputs by clicking the New button. This opens the Define Inputs dialog.
  • You can paste functions by selecting a group from the Function group list and double-clicking the function in the Functions list (or select the function and click the arrow adjacent to the Function group list). Enter any parameters indicated by question marks. The function group labeled All provides a listing of all available functions. A brief description of the currently selected function is displayed in a reserved area in the dialog box.
  • String constants must be enclosed in quotation marks.
  • If values contain decimals, a period (.) must be used as the decimal indicator.

Note: Simulation does not support custom equations with string targets.

To access the Equation Editor

From the menus choose:

Analyze > Simulation...

  1. Click Type in the Equations.
  2. Click the New Equation button on the Model tab.

    Or:

  3. Select the Open in Advanced check box and click Open an Existing Simulation Plan to load a simulation plan that has custom equations.
  4. Click on the Model tab.
  5. Click the New Equation button or select an existing equation and click the Edit button.