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()

1 2	words=lines.flatMap(lambda line:line.lower().split()) words.collect()

4.去掉长度小于3的单词 filter()

1 2	words=lines.flatMap(lambda line:line.lower().split()).filter(lambda line:len(line)>3) words.collect()

5.去掉停用词

1 2	stops= sc.textFile('file:///home/hadoop/stopwords.txt') stops.collect()

1 2	stop = stops.flatMap(lambda line : line.split()).collect() stop

 

1 2	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()

1	words.map(lambda word:(word,1)).collect()

7.统计词频 reduceByKey()

1	words.map(lambda word:(word,1)).reduceByKey(lambda a,b:a+b).collect()

8.按字母顺序排序 sortBy(f)

1	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()

1	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()

1	lines.map(lambda line : line.split(',')[0]).distinct().count()

2.开设了多少门课程？

1	lines.map(lambda line : line.split(',')[1]).distinct().count()

3.每个学生选修了多少门课？map(), countByKey()

1	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()

1	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

1	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

1	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()

1	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()