The Function Tool (Workspace > Tools or press Shift+F8) allows you to create custom functions based on standard correlations or user-defined expressions for a target property.

1. To create a new function, enter the function name in the Function text field. To edit an existing function expression, use the drop-down list to select the target function. Use the toolbar buttons to duplicate, rename or delete an existing function.
2. For a new function, select an appropriate Property type from the drop-down list.
3. Optionally, use the Description field to enter details related to the function.
4. In the Function Expression field, enter the desired function. The constant values in the function should be defined as coefficients while the existing properties or object attributes must be defined as variables.
5. Create a new Variable or edit existing entries, using the variables table and toolbar. Select the property type from the drop-down list.
6. Create a new Coefficient, or edit existing entries, using the coefficients table and toolbar. Select the property type from the drop-down list and enter the value for coefficients in the last column.
Functions with properties (such as temperature and density) that have nonlinear units, like Fahrenheit, dAPI, SGair, etc., should be defined in SI units.
7. The output units must be validated with the resulting dimensions from the function expression. Click Apply to create the function and keep working with the Function Tool or click OK to create the function and exit the form.