使用BigQuery查找带有标准偏差结果并结合WHERE子句的离群值 [英] Using BigQuery to find outliers with standard deviation results combined with WHERE clause

问题描述

标准偏差分析是找到异常值的有用方法.有没有一种方法可以合并该查询的结果(找到远离平均值的第四标准差的值)...

Standard deviation analysis can be a useful way to find outliers. Is there a way to incorporate the result of this query (finding the value of the fourth standard deviation away from the mean)...

SELECT (AVG(weight_pounds) + STDDEV(weight_pounds) * 4) as high FROM [publicdata:samples.natality];

结果= 12.721342001626912

result = 12.721342001626912

...进入另一个查询，该查询生成有关哪些州和日期出生的婴儿最多的信息比平均值高4个标准差?

...Into another query that produces information about which states and dates have the most babies born heavier that 4 standard deviations from average?

SELECT state, year, month ,COUNT(*) AS outlier_count
 FROM [publicdata:samples.natality]
WHERE
  (weight_pounds > 12.721342001626912)
AND
  (state != '' AND state IS NOT NULL)
GROUP BY state, year, month 
ORDER BY outlier_count DESC;

结果:

Row  state   year    month   outlier_count    
1    MD  1990    12  22   
2    NY  1989    10  17   
3    CA  1991    9   14

从本质上讲，最好将其组合成一个查询.

Essentially it would be great to combine this into a single query.

推荐答案

您可以为此滥用JOIN(这样会降低性能):

You can abuse JOIN for this (and thus performance will suffer):

SELECT n.state, n.year, n.month ,COUNT(*) AS outlier_count
FROM (
  SELECT state, year, month, weight_pounds, 1 as key 
  FROM [publicdata:samples.natality]) as n
JOIN (
  SELECT (AVG(weight_pounds) + STDDEV(weight_pounds) * 4) as giant_baby, 
          1 as key 
  FROM [publicdata:samples.natality]) as o
ON n.key = o.key
WHERE
  (n.weight_pounds > o.giant_baby)
AND
  (n.state != '' AND n.state IS NOT NULL)
GROUP BY n.state, n.year, n.month 
ORDER BY outlier_count DESC;

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