25. Parameter Expression Datum Filter¶
The Parameter Expression Datum Filter provides a way to generate filter parameters by evaluating expressions against existing properties. The generated parameters will be available to any further datum filters in the same filter chain.
Tip
Parameters are useful as temporary variables that you want to use during datum processing but do not want to include as datum properties that get posted to SolarNet.
This filter is provided by the Standard Datum Filters plugin.
25.1 Settings¶
Each filter configuration contains the following overall settings:
| Setting | Description |
|---|---|
| Service Name | A unique ID for the filter, to be referenced by other components. |
| Service Group | An optional service group name to assign. |
| Source ID | A case-insensitive pattern to match the input source ID(s) to filter. If omitted then datum for all source ID values will be filtered, otherwise only datum with matching source ID values will be filtered. |
| Required Mode | If configured, an operational mode that must be active for this filter to be applied. |
| Required Tag | Only apply the filter on datum with the given tag. A tag may be prefixed with ! to invert the logic so that the filter only applies to datum without the given tag. Multiple tags can be defined using a , delimiter, in which case at least one of the configured tags must match to apply the filter. |
| Expressions | A list of expression configurations that are evaluated to derive parameter values from other property values. |
Use the + and - buttons to add/remove expression configurations.
25.2 Expression settings¶
Each expression configuration contains the following settings:
| Setting | Description |
|---|---|
| Parameter | The filter parameter name to store the expression result in. |
| Expression | The expression to evaluate. See below for more info. |
| Expression Language | The [expression language][expr-lang] to write Expression in. |
25.3 Expressions¶
See the Expressions section for general expressions reference. This filter supports Datum Expressions that lets you treat all datum properties, and filter parameters, as expression variables directly.