top_comment_phrases.py

   1 from pyspark.sql import functions as f
   2 from pyspark.sql import Window
   3 from pyspark.sql import SparkSession
   4 import numpy as np
   5
   6 spark = SparkSession.builder.getOrCreate()
   7 df = spark.read.text("/gscratch/comdata/users/nathante/reddit_comment_ngrams_10p_sample/")
   8
   9 df = df.withColumnRenamed("value","phrase")
  10
  11
  12 # count overall
  13 N = df.count()
  14 print(f'analyzing PMI on a sample of {N} phrases')
  15 logN = np.log(N)
  16
  17 # count phrase occurrances
  18 phrases = df.groupby('phrase').count()
  19 phrases = phrases.withColumnRenamed('count','phraseCount')
  20 phrases = phrases.withColumn("phraseLogProb", f.log(f.col("phraseCount")) - logN)
  21
  22
  23 # count term occurrances
  24 phrases = phrases.withColumn('terms',f.split(f.col('phrase'),' '))
  25 terms = phrases.select(['phrase','phraseCount','phraseLogProb',f.explode(phrases.terms).alias('term')])
  26
  27 win = Window.partitionBy('term')
  28 terms = terms.withColumn('termCount',f.sum('phraseCount').over(win))
  29 terms = terms.withColumnRenamed('count','termCount')
  30 terms = terms.withColumn('termLogProb',f.log(f.col('termCount')) - logN)
  31
  32 terms = terms.groupBy(terms.phrase, terms.phraseLogProb, terms.phraseCount).sum('termLogProb')
  33 terms = terms.withColumnRenamed('sum(termLogProb)','termsLogProb')
  34 terms = terms.withColumn("phrasePWMI", f.col('phraseLogProb') - f.col('termsLogProb'))
  35
  36 # join phrases to term counts
  37
  38
  39 df = terms.select(['phrase','phraseCount','phraseLogProb','phrasePWMI'])
  40
  41 df = df.repartition('phrasePWMI')
  42 df = df.sort(['phrasePWMI'],descending=True)
  43 df = df.sortWithinPartitions(['phrasePWMI'],descending=True)
  44 df.write.parquet("/gscratch/comdata/users/nathante/reddit_comment_ngrams_pwmi.parquet/",mode='overwrite',compression='snappy')
  45 df.write.csv("/gscratch/comdata/users/nathante/reddit_comment_ngrams_pwmi.csv/",mode='overwrite',compression='none')