CODEWITHSUNDEEP
pythonpython-2.7apache-sparkpyspark
Mohan
Mohan

Reputation: 897

Pyspark - Aggregation on multiple columns

I have data like below. Filename:babynames.csv. 

year    name    percent     sex
1880    John    0.081541    boy
1880    William 0.080511    boy
1880    James   0.050057    boy

I need to sort the input based on year and sex and I want the output aggregated like below (this output is to be assigned to a new RDD). 

year    sex   avg(percentage)   count(rows)
1880    boy   0.070703         3

I am not sure how to proceed after the following step in pyspark. Need your help on this

testrdd = sc.textFile("babynames.csv");
rows = testrdd.map(lambda y:y.split(',')).filter(lambda x:"year" not in x[0])
aggregatedoutput = ????

Upvotes: 25

Views: 116772

Answers (1)

zero323
zero323

Reputation: 330453

  1. Follow the instructions from the README to include spark-csv package

  2. Load data

    df = (sqlContext.read
    .format("com.databricks.spark.csv")
    .options(inferSchema="true", delimiter=";", header="true")
    .load("babynames.csv"))

  3. Import required functions

    from pyspark.sql.functions import count, avg

  4. Group by and aggregate (optionally use Column.alias:

    df.groupBy("year", "sex").agg(avg("percent"), count("*"))

Alternatively:

  • cast percent to numeric
  • reshape to a format ((year, sex), percent)
  • aggregateByKey using pyspark.statcounter.StatCounter

Upvotes: 53

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