Calculated fields can be based on which of the following?

Calculated fields in Splunk are derived from extracted fields, which means they utilize values that have already been parsed from the raw event data. Extracted fields are typically created through field extraction methods such as regex or automatic extraction based on data formats. This means that they contain meaningful data that has been identified and made available for additional processing.

When calculating fields, it's essential to build upon existing data that has already been captured from the events. Extracted fields serve as a foundation because they represent the structured data extracted from unstructured log data, allowing for complex calculations, concatenations, or transformations to create new fields.

Other choices, such as tags or output fields from a lookup, do not directly relate to the basis for calculated fields. Tags are used for categorizing events and improving searches rather than serving as values for calculations. Output fields for a lookup are generated based on certain lookup operations but don't serve as the basis for calculated fields either. Lastly, fields generated from a search string refer to temporary fields created during a specific search but are not saved as part of the indexed data structure on which calculated fields depend. Thus, they do not provide a reliable basis for creating calculated fields.