如何计算基于组的分位数？

Posted 2023-04-15

【中文标题】如何计算基于组的分位数？

【英文标题】：How to calculate group-based quantiles?

【发布时间】：2020-03-06 11:54:53

【问题描述】：

我正在使用 spark-sql-2.4.1v，我正在尝试在给定数据的每一列上查找分位数，即百分位数 0、百分位数 25 等。

我的数据框df：

+----+---------+-------------+----------+-----------+--------+
|  id|     date|      revenue|con_dist_1| con_dist_2| state  |
+----+---------+-------------+----------+-----------+--------+
|  10|1/15/2018|  0.010680705|         6|0.019875458|   TX   |
|  10|1/15/2018|  0.006628853|         4|0.816039063|   AZ   |
|  10|1/15/2018|   0.01378215|         4|0.082049528|   TX   |
|  10|1/15/2018|  0.010680705|         6|0.019875458|   TX   |
|  10|1/15/2018|  0.006628853|         4|0.816039063|   AZ   |
+----+---------+-------------+----------+-----------+--------+

如何找到每个州的“con_dist_1”和“con_dist_2”列上的分位数？

【问题讨论】：

相关问题：***.com/questions/46845672/…

【参考方案1】：

可能的解决方案是：

scala> input.show
+---+---------+-----------+----------+-----------+-----+
| id|     date|    revenue|con_dist_1| con_dist_2|state|
+---+---------+-----------+----------+-----------+-----+
| 10|1/15/2018|0.010680705|         6|0.019875458|   TX|
| 10|1/15/2018|0.006628853|         4|0.816039063|   AZ|
| 10|1/15/2018| 0.01378215|         4|0.082049528|   TX|
| 10|1/15/2018|0.010680705|         6|0.019875458|   TX|
| 10|1/15/2018|0.006628853|         4|0.816039063|   AZ|
+---+---------+-----------+----------+-----------+-----+

scala> val df1 = input.groupBy("state").agg(collect_list("con_dist_1").as("combined_1"), collect_list("con_dist_2").as("combined_2"))
df1: org.apache.spark.sql.DataFrame = [state: string, combined_1: array<int> ... 1 more field]

scala> df1.show
+-----+----------+--------------------+                                         
|state|combined_1|          combined_2|
+-----+----------+--------------------+
|   AZ|    [4, 4]|[0.816039063, 0.8...|
|   TX| [6, 4, 6]|[0.019875458, 0.0...|
+-----+----------+--------------------+

scala> df1.
     | withColumn("comb1_Q1", sort_array($"combined_1")(((size($"combined_1")-1)*0.25).cast("int"))).
     | withColumn("comb1_Q2", sort_array($"combined_1")(((size($"combined_1")-1)*0.5).cast("int"))).
     | withColumn("comb1_Q3", sort_array($"combined_1")(((size($"combined_1")-1)*0.75).cast("int"))).
     | withColumn("comb_2_Q1", sort_array($"combined_2")(((size($"combined_2")-1)*0.25).cast("int"))).
     | withColumn("comb_2_Q2", sort_array($"combined_2")(((size($"combined_2")-1)*0.5).cast("int"))).
     | withColumn("comb_2_Q3", sort_array($"combined_2")(((size($"combined_2")-1)*0.75).cast("int"))).
     | show
+-----+----------+--------------------+--------+--------+--------+-----------+-----------+-----------+
|state|combined_1|          combined_2|comb1_Q1|comb1_Q2|comb1_Q3|  comb_2_Q1|  comb_2_Q2|  comb_2_Q3|
+-----+----------+--------------------+--------+--------+--------+-----------+-----------+-----------+
|   AZ|    [4, 4]|[0.816039063, 0.8...|       4|       4|       4|0.816039063|0.816039063|0.816039063|
|   TX| [6, 4, 6]|[0.019875458, 0.0...|       4|       6|       6|0.019875458|0.019875458|0.019875458|
+-----+----------+--------------------+--------+--------+--------+-----------+-----------+-----------+

编辑

我不认为我们可以使用 approx quantile 方法来实现，因为您需要在 state 列上分组并聚合 con_dist 列和 approx quantile 期望一整列整数或浮点数，但不是数组类型。

另一种解决方案是使用spark-sql，如下图：

scala> input.show
+---+---------+-----------+----------+-----------+-----+
| id|     date|    revenue|con_dist_1| con_dist_2|state|
+---+---------+-----------+----------+-----------+-----+
| 10|1/15/2018|0.010680705|         6|0.019875458|   TX|
| 10|1/15/2018|0.006628853|         4|0.816039063|   AZ|
| 10|1/15/2018| 0.01378215|         4|0.082049528|   TX|
| 10|1/15/2018|0.010680705|         6|0.019875458|   TX|
| 10|1/15/2018|0.006628853|         4|0.816039063|   AZ|
+---+---------+-----------+----------+-----------+-----+


scala> input.createOrReplaceTempView("input")

scala> :paste
// Entering paste mode (ctrl-D to finish)

val query = "select state, percentile_approx(con_dist_1,0.25) as col1_quantile_1, " +
  "percentile_approx(con_dist_1,0.5) as col1_quantile_2," +
  "percentile_approx(con_dist_1,0.75) as col1_quantile_3, " +
  "percentile_approx(con_dist_2,0.25) as col2_quantile_1,"+
  "percentile_approx(con_dist_2,0.5) as col2_quantile_2," +
  "percentile_approx(con_dist_2,0.75) as col2_quantile_3 " +
  "from input group by state"

// Exiting paste mode, now interpreting.

query: String = select state, percentile_approx(con_dist_1,0.25) as col1_quantile_1, percentile_approx(con_dist_1,0.5) as col1_quantile_2,percentile_approx(con_dist_1,0.75) as col1_quantile_3, percentile_approx(con_dist_2,0.25) as col2_quantile_1,percentile_approx(con_dist_2,0.5) as col2_quantile_2,percentile_approx(con_dist_2,0.75) as col2_quantile_3 from input group by state

scala> val df2 = spark.sql(query)
df2: org.apache.spark.sql.DataFrame = [state: string, col1_quantile_1: int ... 5 more fields]

scala> df2.show
+-----+---------------+---------------+---------------+---------------+---------------+---------------+
|state|col1_quantile_1|col1_quantile_2|col1_quantile_3|col2_quantile_1|col2_quantile_2|col2_quantile_3|
+-----+---------------+---------------+---------------+---------------+---------------+---------------+
|   AZ|              4|              4|              4|    0.816039063|    0.816039063|    0.816039063|
|   TX|              4|              6|              6|    0.019875458|    0.019875458|    0.082049528|
+-----+---------------+---------------+---------------+---------------+---------------+---------------+

如果有帮助请告诉我！！

【讨论】：

@BdEngineer 是的，您可以将其保存在循环内，但通常情况下，您可以在循环外创建临时视图。由于只是一个视图，所以可以替换。

是的，输入视图将被覆盖。这取决于您从中创建视图的数据框