Editing equation-based functional data

Equation-based functional attributes (GRANTA MI Equations and Logic attribute type) store numerical data as an expression that describes how the attribute value varies dependent on one or more parameters.

To edit the data for an equation-based functional attribute, click Edit this data near the attribute name on the datasheet. In a version-controlled table, this option is only available on unreleased records.

To edit equation-based functional data

1. Ensure that the system is in Edit Mode.
2. Open the datasheet of interest and click Edit this data on the left of the attribute name.
3. The attribute may already contain one or more pre-configured expressions; depending on how your database has been configured, you may be able to define a new expression or choose an alternative expression on the Data>Expression tab; see Editing the expression below.
4. To specify the graph axes, on the Data>Expression tab:
   • Default X axis parameter: select the parameter to use as the default x-axis.

     For constant expressions: you can select No Free Parameter (Unbound all parameters) here and then set the bound/unbound value for each one on the Parameter Extents tab.

   • Transpose axes by default: Select or clear the check box to transpose the graph axes. When the graph axes are transposed, the attribute value is plotted on the x-axis, and the parameter value on the y-axis.
5. To specify the parameter ranges over which the expression is valid, click on the Data>Parameter Extents tab; see Defining the parameter extents below.
6. To add, remove, or modify the curves in the graph, click on the Curves tab.
7. (Optional) You may be able to add metadata, such as statistical information or notes about the source of the data.
8. (Optional) You can add information about any changes that you make on the Notes tab.
9. Click Save to save all your changes.

Editing the expression

The Expression and Domain list on the Expression tab will include any alternative, compatible expressions defined in the attribute (From attribute) or table (From table), if this has been configured by the GRANTA database administrator.

Equation-based functional attributes may be set up to allow you to define a new expression to derive the attribute values, instead of using a pre-existing expression; if this has been configured by the Granta database administrator in MI:Admin, a User defined expression option will appear in the Expression and Domain list.

Expressions can be constructed from attributes, constants, parameters, and functions. Expressions are specific to a table in a database; an expression used for an equation-based attribute in a particular table must be defined specifically for that table, and cannot include attributes, constants, or parameters from other tables. However, it may be used by several attributes in that table.

The calculation of expressions is performed in database units. The result will then be converted to the relevant display unit, if it is different.

See the help for MI:Admin for detailed information about expressions and functions in GRANTA MI.

Defining the parameter extents

The parameter extents define the parameter space over which an expression is valid.

For example, we could define an expression to calculate strain as [ stress / Youngs Modulus ]. This would hold for values of 0 < stress < yield-stress-for-material. So we can define the parameter extent for stress as 0 to yield-stress-for-material.

You can define the parameter ranges over which an expression is valid on the Data>Parameter Extents tab.

Select Unbound to mark a parameter that is not included in the expression as applicable over all possible values; note that parameters included in the expression must be bounded.

Adding, removing, and modifying curves

On the Data>Curves tab, you can add and remove curves and, for each curve, you can:

• Specify the parameter values used to calculate the curve.
• Identify it as the default curve.
• Optionally, specify a label for the curve that will appear in the graph legend.