Apache spark 为什么dropna()不起作用?
系统:Cloudera Quickstart VM 5.4上的Spark 1.3.0(Anaconda Python dist.) 以下是Spark数据框:Apache spark 为什么dropna()不起作用?,apache-spark,pyspark,cloudera-quickstart-vm,Apache Spark,Pyspark,Cloudera Quickstart Vm,系统:Cloudera Quickstart VM 5.4上的Spark 1.3.0(Anaconda Python dist.) 以下是Spark数据框: from pyspark.sql import SQLContext from pyspark.sql.types import * sqlContext = SQLContext(sc) data = sc.parallelize([('Foo',41,'US',3), ('Foo',39,
from pyspark.sql import SQLContext
from pyspark.sql.types import *
sqlContext = SQLContext(sc)
data = sc.parallelize([('Foo',41,'US',3),
('Foo',39,'UK',1),
('Bar',57,'CA',2),
('Bar',72,'CA',3),
('Baz',22,'US',6),
(None,75,None,7)])
schema = StructType([StructField('Name', StringType(), True),
StructField('Age', IntegerType(), True),
StructField('Country', StringType(), True),
StructField('Score', IntegerType(), True)])
df = sqlContext.createDataFrame(data,schema)
data.show()
然而,这两种方法都不管用
df.dropna()
df.na.drop()
我得到这个信息:
>>> df.show()
Name Age Country Score
Foo 41 US 3
Foo 39 UK 1
Bar 57 CA 2
Bar 72 CA 3
Baz 22 US 6
null 75 null 7
>>> df.dropna().show()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/spark/python/pyspark/sql/dataframe.py", line 580, in __getattr__
jc = self._jdf.apply(name)
File "/usr/lib/spark/python/lib/py4j-0.8.2.1-src.zip/py4j/java_gateway.py", line 538, in __call__
File "/usr/lib/spark/python/lib/py4j-0.8.2.1-src.zip/py4j/protocol.py", line 300, in get_return_value
py4j.protocol.Py4JJavaError: An error occurred while calling o50.apply.
: org.apache.spark.sql.AnalysisException: Cannot resolve column name "dropna" among (Name, Age, Country, Score);
at org.apache.spark.sql.DataFrame$$anonfun$resolve$1.apply(DataFrame.scala:162)
at org.apache.spark.sql.DataFrame$$anonfun$resolve$1.apply(DataFrame.scala:162)
at scala.Option.getOrElse(Option.scala:120)
at org.apache.spark.sql.DataFrame.resolve(DataFrame.scala:161)
at org.apache.spark.sql.DataFrame.col(DataFrame.scala:436)
at org.apache.spark.sql.DataFrame.apply(DataFrame.scala:426)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:231)
at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:379)
at py4j.Gateway.invoke(Gateway.java:259)
at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:133)
at py4j.commands.CallCommand.execute(CallCommand.java:79)
at py4j.GatewayConnection.run(GatewayConnection.java:207)
at java.lang.Thread.run(Thread.java:745)
df.show()
姓名年龄国家分数
富41美3
富39英国1
酒吧57 CA 2
Bar 72 CA 3
巴兹22美6
零75零7
>>>df.dropna().show()
回溯(最近一次呼叫最后一次):
文件“”,第1行,在
文件“/usr/lib/spark/python/pyspark/sql/dataframe.py”,第580行,在__
jc=self.\u jdf.apply(名称)
文件“/usr/lib/spark/python/lib/py4j-0.8.2.1-src.zip/py4j/java_gateway.py”,第538行,在调用中__
文件“/usr/lib/spark/python/lib/py4j-0.8.2.1-src.zip/py4j/protocol.py”,第300行,在get_return_值中
py4j.protocol.Py4JJavaError:调用o50.apply时出错。
:org.apache.spark.sql.AnalysisException:无法解析(姓名、年龄、国家/地区、分数)中的列名“dropna”;
位于org.apache.spark.sql.DataFrame$$anonfun$resolve$1.apply(DataFrame.scala:162)
位于org.apache.spark.sql.DataFrame$$anonfun$resolve$1.apply(DataFrame.scala:162)
在scala.Option.getOrElse(Option.scala:120)
位于org.apache.spark.sql.DataFrame.resolve(DataFrame.scala:161)
位于org.apache.spark.sql.DataFrame.col(DataFrame.scala:436)
位于org.apache.spark.sql.DataFrame.apply(DataFrame.scala:426)
在sun.reflect.NativeMethodAccessorImpl.invoke0(本机方法)处
在sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)中
在sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)中
位于java.lang.reflect.Method.invoke(Method.java:606)
位于py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:231)
位于py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:379)
在py4j.Gateway.invoke处(Gateway.java:259)
位于py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:133)
在py4j.commands.CallCommand.execute(CallCommand.java:79)
在py4j.GatewayConnection.run处(GatewayConnection.java:207)
运行(Thread.java:745)
还有其他人遇到过这个问题吗?解决办法是什么?Pyspark似乎是我在寻找一个名为“na”的专栏。任何帮助都将不胜感激 tl;dr方法
na
和dropna
仅从Spark 1.3.1开始提供
你犯了几个错误:
data=sc.parallelize([..('',75',,7)]
,您打算使用''
表示无
,但是,它只是一个字符串而不是nullna
和dropna
都是数据帧类上的方法,因此,您应该使用df
调用它data=sc.parallelize([('Foo',41,'US',3),
('Foo',39,'UK',1),
('Bar',57,'CA',2),
('Bar',72,'CA',3),
('Baz',22,'US',6),
(无,75,无,7)])
schema=StructType([StructField('Name',StringType(),True),
StructField('Age',IntegerType(),True),
StructField('Country',StringType(),True),
StructField('Score',IntegerType(),True)])
df=sqlContext.createDataFrame(数据,模式)
df.dropna().show()
df.na.drop().show()
我意识到这个问题是一年前提出的,以防将解决方案留给Scala,下面是以防有人来到这里寻找相同的解决方案
val data = sc.parallelize(List(("Foo",41,"US",3), ("Foo",39,"UK",1),
("Bar",57,"CA",2), ("Bar",72,"CA",3), ("Baz",22,"US",6), (None, 75,
None, 7)))
val schema = StructType(Array(StructField("Name", StringType, true),
StructField("Age", IntegerType, true), StructField("Country",
StringType, true), StructField("Score", IntegerType, true)))
val dat = data.map(d => Row(d._1, d._2, d._3, d._4))
val df = sqlContext.createDataFrame(dat, schema)
df.na.drop()
注:
上述解决方案仍然无法在Scala中给出正确的结果,不确定Scala和python绑定的实现有什么不同。如果丢失的数据表示为null,则na.drop有效。对于“”和None,它失败。另一种方法是使用withColumn函数来处理不同形式的缺失值
val data = sc.parallelize(List(("Foo",41,"US",3), ("Foo",39,"UK",1),
("Bar",57,"CA",2), ("Bar",72,"CA",3), ("Baz",22,"US",6), (None, 75,
None, 7)))
val schema = StructType(Array(StructField("Name", StringType, true),
StructField("Age", IntegerType, true), StructField("Country",
StringType, true), StructField("Score", IntegerType, true)))
val dat = data.map(d => Row(d._1, d._2, d._3, d._4))
val df = sqlContext.createDataFrame(dat, schema)
df.na.drop()