RDD编程
一、词频统计:
1.读文本文件生成RDD lines
lines = sc.textFile('file:///home/hadoop/file')
lines.collect()
2.将一行一行的文本分割成单词 words flatmap()
words=lines.flatMap(lambda line:line.split())
words.collect()
3.全部转换为小写 lower()
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words = lines.flatMap( lambda line:line.lower().split()) words.collect() |
4.去掉长度小于3的单词 filter()
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words = lines.flatMap( lambda line:line.lower().split()). filter ( lambda line: len (line)> 3 ) words.collect() |
5.去掉停用词
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stops = sc.textFile( 'file:///home/hadoop/stopwords.txt' ) stops.collect() |
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stop = stops.flatMap( lambda line : line.split()).collect() stop |
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words = lines.flatMap( lambda line:line.lower().split()). filter ( lambda word:word not in stop) words.collect() |
6.转换成键值对 map()
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words. map ( lambda word:(word, 1 )).collect() |
7.统计词频 reduceByKey()
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words. map ( lambda word:(word, 1 )).reduceByKey( lambda a,b:a + b).collect() |
8.按字母顺序排序 sortBy(f)
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words. map ( lambda word:(word, 1 )).reduceByKey( lambda a,b:a + b).sortBy( lambda word:word[ 0 ]).collect() |
9.按词频排序 sortByKey()
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words. map ( lambda word:(word, 1 )).reduceByKey( lambda a,b:a + b).sortByKey().collect() |
二、学生课程分数案例
1.总共有多少学生?map(), distinct(), count()
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lines. map ( lambda line : line.split( ',' )[ 0 ]).distinct().count() |
2.开设了多少门课程?
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lines. map ( lambda line : line.split( ',' )[ 1 ]).distinct().count() |
3.每个学生选修了多少门课?map(), countByKey()
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lines. map ( lambda line : line.split( ',' )). map ( lambda line:(line[ 0 ],(line[ 1 ],line[ 2 ]))).countByKey() |
4.每门课程有多少个学生选?map(), countByValue()
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lines. map ( lambda line : line.split( ',' )). map ( lambda line : (line[ 1 ])).countByValue() |
5.Tom选修了几门课?每门课多少分?filter(), map() RDD
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lines. filter ( lambda line: "Tom" in line). map ( lambda line:line.split( ',' )).collect() |
6.Tom选修了几门课?每门课多少分?map(),lookup() list
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lines. map ( lambda line:line.split( ',' )). map ( lambda line:(line[ 0 ],(line[ 1 ],line[ 2 ]))).lookup( "Tom" ) |
7.Tom的成绩按分数大小排序。filter(), map(), sortBy()
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lines. filter ( lambda line: "Tom" in line). map ( lambda line:line.split( ',' )).sortBy( lambda line:(line[ 2 ])).collect() |
8.Tom的平均分。map(),lookup(),mean()