Question

我按日期列对行进行分组时，尝试显示列中的最大值。

所以我尝试了这段代码

maxVal = dfSelect.select('*')\
            .groupBy('DATE')\
            .agg(max('CLOSE'))

但是输出看起来像这样：

+----------+----------+
|      DATE|max(CLOSE)|
+----------+----------+
|1987-05-08|     43.51|
|1987-05-29|    39.061|
+----------+----------+

我想像下面这样输出

+------+---+----------+------+------+------+------+------+---+----------+
|TICKER|PER|      DATE|  TIME|  OPEN|  HIGH|   LOW| CLOSE|VOL|max(CLOSE)|
+------+---+----------+------+------+------+------+------+---+----------+
|   CDG|  D|1987-01-02|000000|50.666|51.441|49.896|50.666|  0|    50.666|
|   ABC|  D|1987-01-05|000000|51.441| 52.02|51.441|51.441|  0|    51.441|
+------+---+----------+------+------+------+------+------+---+----------+

所以我的问题是如何将代码更改为具有所有列和汇总的“ CLOSE”列的输出？

我的数据格式如下：

root
 |-- TICKER: string (nullable = true)
 |-- PER: string (nullable = true)
 |-- DATE: date (nullable = true)
 |-- TIME: string (nullable = true)
 |-- OPEN: float (nullable = true)
 |-- HIGH: float (nullable = true)
 |-- LOW: float (nullable = true)
 |-- CLOSE: float (nullable = true)
 |-- VOL: integer (nullable = true)
 |-- OPENINT: string (nullable = true)

Answer 1

如果要对原始数据框中的所有列进行相同的聚合，则可以执行类似的操作

import pyspark.sql.functions as F
expr = [F.max(coln).alias(coln) for coln in df.columns if 'date' not in coln] # df is your datafram
df_res = df.groupby('date').agg(*expr)

如果您想要多个聚合，则可以这样做，

sub_col1 = # define
sub_col2=# define
expr1 = [F.max(coln).alias(coln) for coln in sub_col1 if 'date' not in coln]
expr2 = [F.first(coln).alias(coln) for coln in sub_col2 if 'date' not in coln]
expr=expr1+expr2
df_res = df.groupby('date').agg(*expr)

如果只希望汇总一列并添加到原始数据框中，则可以在汇总后进行自联接

df_agg = df.groupby('date').agg(F.max('close').alias('close_agg')).withColumn("dummy",F.lit("dummmy")) # dummy column is needed as a workaround in spark issues of self join
df_join = df.join(df_agg,on='date',how='left')

或者您可以使用开窗功能

from pyspark.sql import Window
w= Window.partitionBy('date')
df_res = df.withColumn("max_close",F.max('close').over(w))

汇总一列，但显示选择中的所有列

1 个答案: