Pyspark:计算连续观察的条纹 [英] Pyspark: Calculate streak of consecutive observations

问题描述

我有一个Spark(2.4.0)数据框，其中的列只有两个值( 0 或 1 ).我需要计算此数据中连续 0 s和 1 s的条纹，如果值更改，则将条纹重置为零.

I have a Spark (2.4.0) data frame with a column that has just two values (either 0 or 1). I need to calculate the streak of consecutive 0s and 1s in this data, resetting the streak to zero if the value changes.

一个例子:

from pyspark.sql import (SparkSession, Window)
from pyspark.sql.functions import (to_date, row_number, lead, col)

spark = SparkSession.builder.appName('test').getOrCreate()

# Create dataframe
df = spark.createDataFrame([
    ('2018-01-01', 'John', 0, 0),
    ('2018-01-01', 'Paul', 1, 0),
    ('2018-01-08', 'Paul', 3, 1),
    ('2018-01-08', 'Pete', 4, 0),
    ('2018-01-08', 'John', 3, 0),
    ('2018-01-15', 'Mary', 6, 0),
    ('2018-01-15', 'Pete', 6, 0),
    ('2018-01-15', 'John', 6, 1),
    ('2018-01-15', 'Paul', 6, 1),
], ['str_date', 'name', 'value', 'flag'])

df.orderBy('name', 'str_date').show()
## +----------+----+-----+----+
## |  str_date|name|value|flag|
## +----------+----+-----+----+
## |2018-01-01|John|    0|   0|
## |2018-01-08|John|    3|   0|
## |2018-01-15|John|    6|   1|
## |2018-01-15|Mary|    6|   0|
## |2018-01-01|Paul|    1|   0|
## |2018-01-08|Paul|    3|   1|
## |2018-01-15|Paul|    6|   1|
## |2018-01-08|Pete|    4|   0|
## |2018-01-15|Pete|    6|   0|
## +----------+----+-----+----+

使用此数据，我想计算连续的零和一的连胜纪录，按日期排序并按名称显示在窗口中":

With this data, I'd like to calculate the streak of consecutive zeros and ones, ordered by date and "windowed" by name:

# Expected result:
## +----------+----+-----+----+--------+--------+
## |  str_date|name|value|flag|streak_0|streak_1|
## +----------+----+-----+----+--------+--------+
## |2018-01-01|John|    0|   0|       1|       0|
## |2018-01-08|John|    3|   0|       2|       0|
## |2018-01-15|John|    6|   1|       0|       1|
## |2018-01-15|Mary|    6|   0|       1|       0|
## |2018-01-01|Paul|    1|   0|       1|       0|
## |2018-01-08|Paul|    3|   1|       0|       1|
## |2018-01-15|Paul|    6|   1|       0|       2|
## |2018-01-08|Pete|    4|   0|       1|       0|
## |2018-01-15|Pete|    6|   0|       2|       0|
## +----------+----+-----+----+--------+--------+

当然，如果'flag'改变，我需要连胜将自己重置为零.

Of course, I would need the streak to reset itself to zero if the 'flag' changes.

有没有办法做到这一点?

Is there a way of doing this?

推荐答案

这将要求先对具有相同值的第一组连续行使用行号方法，然后在各组之间使用排名方法.

This would require a difference in row numbers approach to first group consecutive rows with the same value and then using a ranking approach among the groups.

from pyspark.sql import Window 
from pyspark.sql import functions as f
#Windows definition
w1 = Window.partitionBy(df.name).orderBy(df.date)
w2 = Window.partitionBy(df.name,df.flag).orderBy(df.date)

res = df.withColumn('grp',f.row_number().over(w1)-f.row_number().over(w2))
#Window definition for streak
w3 = Window.partitionBy(res.name,res.flag,res.grp).orderBy(res.date)
streak_res = res.withColumn('streak_0',f.when(res.flag == 1,0).otherwise(f.row_number().over(w3))) \
                .withColumn('streak_1',f.when(res.flag == 0,0).otherwise(f.row_number().over(w3)))
streak_res.show()

这篇关于Pyspark:计算连续观察的条纹的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！