Function aggregate_values_k 

pub fn aggregate_values_k(
    function_num: u32,
    values: &[Value],
    k: &Value,
) -> Value

AGGREGATE codes 14 = LARGE, 15 = SMALL, 16 = PERCENTILE.INC, 17 = QUARTILE.INC, 18 = PERCENTILE.EXC, 19 = QUARTILE.EXC with their k argument; codes 1–13 delegate to aggregate_values.