用于计算偏度和峰度的plpgsql Postgresql函数

CREATE OR REPLACE FUNCTION calculate_skewness_kurtosis(data numeric[])
RETURNS TABLE(skewness numeric, kurtosis numeric) AS $$
DECLARE
    n int;
    mean numeric;
    variance numeric;
    skewness_result numeric;
    kurtosis_result numeric;
BEGIN
    SELECT COUNT(*), AVG(val), VARIANCE(val)
    INTO n, mean, variance
    FROM unnest(data) AS val;

    SELECT SUM(POWER(val - mean, 3))
    INTO skewness_result
    FROM unnest(data) AS val;

    SELECT SUM(POWER(val - mean, 4))
    INTO kurtosis_result
    FROM unnest(data) AS val;

    skewness_result := skewness_result / (n * POWER(variance, 1.5));
    kurtosis_result := kurtosis_result / (n * POWER(variance, 2)) - 3;

    RETURN QUERY SELECT skewness_result, kurtosis_result;
END;
$$ LANGUAGE plpgsql;

SELECT skewness, kurtosis
FROM calculate_skewness_kurtosis(ARRAY[1, 2, 3, 4, 5]);