How do I write an Excel array formula to extract unique items from a list if a condition is met in a column next to the list?
If you have Microsoft 365 or Excel 2021, you have the FILTER and UNIQUE functions. To return unique items from column B when column D is greater than 5, you might use:
If you have an older version of Excel, you may use INDEX, AGGREGATE & MATCH (requires Excel 2010 or later) in a rather ungainly formula. You might need to array-enter this formula (Control + Shift + Enter).
If you are stuck with Excel 2007, God bless. But you can use a vaguely similar array-entered formula using LARGE instead of AGGREGATE. Note that it returns the unique items from the bottom of the list first.