Question

我想要每个小组中最常上的课。每个组中可以有多个行，也可以有多个类。我们可以忽略领带的问题，因为此python应该自动接受第一堂课。

我尝试将rdd更改为触发数据帧，然后使用来自以下链接pyspark: aggregate on the most frequent value in a column的代码

但是我尝试不将数据转换为SparkDataframe

下面是数据集

Data= sc.parallelize([(1, 'class1', 0.0),
       (1, 'class1', 2.9870435922860854),
       (1, 'class1', 3.1390539564237088),
       (2, 'class1', 1.8147552294243288),
       (2, 'class1', 2.2762141107738643),
       (2, 'class1', 2.3276650040679754),
       (3, 'class1', 2.1916602976063415),
       (3, 'class2', 2.8092745089004265),
       (3, 'class2', 2.962653217205646),
       (4, 'class2', 1.9684050295783773),
       (4, 'class2', 2.6954556024643974),
       (4, 'class1', 2.849277442723792),
       (5, 'class2', 2.42178294501635),
       (5, 'class2', 3.650846798310411),
       (5, 'class1', 4.209012410198228),
       (6, 'class1', 1.942895930291406),
       (6, 'class1', 2.3133629778496676),
       (6, 'class2', 3.0147225096785264),
       (7, 'class1', 1.7185194340256884),
       (7, 'class1', 2.91322741107079),
       (7, 'class1', 3.5767422323347633),
       (8, 'class1', 2.4711392945465893),
       (8, 'class1', 3.436547108084221),
       (8, 'class1', 3.937683211352823),
       (9, 'class1', 3.800013103330196),
       (9, 'class1', 4.632413017908266),
       (9, 'class1', 5.191184050603831),

预期产量

  [(1, Class1),(2,Class1),(3,Class2),(4,Class2),(5,Class2),(6,Class1),(7,Class1),(8,Class1),(9,Class1)]

另外，我可能有多个班级。

每行中的第一个元素是组ID，第二个元素是类，第三个元素只是距离，我认为这实际上并没有多大用处。

Answer 1

这是pyspark的RDD解决方案

>>> rddMap1 = Data.map(lambda x: (str(x[0])+','+x[1],float(x[2])))
>>> rddMap1.first()
('1,class1', 0.0)
>>> 
>>> rddReduce1 = rddMap1.reduceByKey(lambda x,y: x+y)
>>> rddReduce1.first()
('1,class1', 6.126097548709794)
>>> 
>>> rddMap2 = rddReduce1.map(lambda x: (int(x[0].split(',')[0]),(x[0].split(',')[1],x[1])))
>>> rddMap2.first()
(1, ('class1', 6.126097548709794))
>>> 
>>> rddReduce2 = rddMap2.reduceByKey(lambda x,y: x if x[1] > y[1] else y)
>>> rddReduce2.first()
(1, ('class1', 6.126097548709794))
>>> 
>>> rddReduce2.map(lambda x: (x[0],x[1][0])).collect()
[(1, 'class1'), (2, 'class1'), (3, 'class2'), (4, 'class2'), (5, 'class2'), (6, 'class1'), (7, 'class1'), (8, 'class1'), (9, 'class1')]

Answer 2

from operator import add
from operator import itemgetter

data= sc.parallelize([
   (1, 'class1', 0.0),
   (1, 'class1', 2.9870435922860854),
   (1, 'class1', 3.1390539564237088),
   (2, 'class1', 1.8147552294243288),
   (2, 'class1', 2.2762141107738643),
   (2, 'class1', 2.3276650040679754),
   (3, 'class1', 2.1916602976063415),
   (3, 'class1', 2.1916602976063415),
   (3, 'class1', 2.1916602976063415),
   (3, 'class2', 2.8092745089004265),
   (3, 'class2', 2.962653217205646),
   (3, 'class4', 1.9684050295783773),
   (3, 'class4', 2.6954556024643974),
   (3, 'class4', 2.849277442723792),
   (3, 'class4', 2.42178294501635),
   (5, 'class2', 3.650846798310411),
   (5, 'class1', 4.209012410198228),
   (6, 'class1', 1.942895930291406),
   (6, 'class1', 2.3133629778496676),
   (6, 'class2', 3.0147225096785264),
   (7, 'class1', 1.7185194340256884),
   (7, 'class1', 2.91322741107079),
   (7, 'class1', 3.5767422323347633),
   (8, 'class1', 2.4711392945465893)
                 ])

data2 = data.map(lambda x: ((x[0],x[1]), 1)).reduceByKey(add).map(lambda x: ((x[0][0]),(x[0][1],x[1]))).groupByKey().mapValues(list)

data3 = data2.map(lambda (k, l): (k, sorted(l, key=itemgetter(1), reverse=True)))

data4 = data3.mapValues(lambda x: (x[0]))

返回：

[(8, ('class1', 1)), (1, ('class1', 3)), (2, ('class1', 3)), (3, ('class4', 4)), (5, ('class1', 1)), (6, ('class1', 2)), (7, ('class1', 3))]

每天都给我Scala！

领带不符合要求。不知道您将如何做，如果真的做了，真正的好处还不是那么明显。

PySpark rdd中按组划分的最频繁的类，但不转换为Spark Dataframe

2 个答案: