FILTER
Requires: Write access to configure a questionnaire calculation.
Keeps selected inputs or matching text items. Input/output: any records in whole-input mode; text lists in Per item mode.
With Per item off, keeps only explicitly selected keys; an empty selection keeps nothing. With it on, keeps text items present in the operand lists. Example: ['walk','rest'] filtered by ['rest'] gives ['rest'].
If none of the requested operands exists, the original text is retained. An existing but empty operand yields an empty match list. This differs from an ordinary numeric threshold.