ported/rank_common

pub fn rank_eq(number: f64, values: &[f64], order: RankOrder) -> Result<f64, WorksheetErrorCode> {
    if values.is_empty() {
        return Err(WorksheetErrorCode::NA);
    }
    let matches = values.iter().filter(|value| **value == number).count();
    if matches == 0 {
        return Err(WorksheetErrorCode::NA);
    }

    let rank = match order {
        RankOrder::Descending => values.iter().filter(|value| **value > number).count() + 1,
        RankOrder::Ascending => values.iter().filter(|value| **value < number).count() + 1,
    };
    Ok(rank as f64)
}

pub fn rank_avg(number: f64, values: &[f64], order: RankOrder) -> Result<f64, WorksheetErrorCode> {
    let first = rank_eq(number, values, order)?;
    let matches = values.iter().filter(|value| **value == number).count() as f64;
    Ok(first + (matches - 1.0) / 2.0)
}