Use the CASE Statement to convert data elements:

Add a field in your DataSource  to use the CASE function.

Sample:

CASE
WHEN REGEXP_MATCH(Grade_Level, "9") THEN "Freshman"
WHEN REGEXP_MATCH(Grade_Level, "10") THEN "Sophomore"
ELSE "Other"
END

 

CASE
WHEN REGEXP_MATCH(Grade_Level, "9") THEN "Freshman"
WHEN REGEXP_MATCH(Grade_Level, "10") THEN "Sophomore"
ELSE "Other"
END