REPEAT function for Excel

excel-lambda-repeat.txt

REPEAT = LAMBDA(table,row_repeats,[has_header],

    LET(
        // if has_header is zero, FALSE or is omitted, then FALSE, otherwise TRUE
        // long-hand for clarity!
        _has_header,IF(OR(has_header=0,ISOMITTED(has_header),has_header=FALSE),FALSE,TRUE),
        _header,IF(_has_header,TAKE(table,1),NA()), // get the header if it's there
        _table,IF(_has_header,DROP(table,1),table), // redefine the table based on header presence
        _reps,NUMBERVALUE(row_repeats),
        _total,SUM(_reps),
        IF(
            OR(
                MIN(_reps)<0, // negatives not allowed
                _total=0, // all zero not allowed
                ROWS(_table)<>ROWS(_reps) // must be same size as table
            ),
            #VALUE!, // return an error if any of the above conditions are true
            LET(
                // create an index array to pull rows multiple times from the input table
                _data,INDEX(
                    _table,
                    XMATCH(SEQUENCE(_total),SCAN(,_reps,SUM),1),
                    SEQUENCE(,COLUMNS(_table))
                ),
                // stack the header on top... or not
                IF(_has_header,VSTACK(_header,_data),_data)
            )
        )
    )

);