df = df.withColumnRenamed("value","phrase")
+# count phrase occurrances
+phrases = df.groupby('phrase').count()
+phrases = phrases.withColumnRenamed('count','phraseCount')
+phrases = phrases.filter(phrases.phraseCount > 10)
+
# count overall
-N = df.count()
+N = phrases.select(f.sum(phrases.phraseCount).alias("phraseCount")).collect()[0].phraseCount
+
print(f'analyzing PMI on a sample of {N} phrases')
logN = np.log(N)
-
-# count phrase occurrances
-phrases = df.groupby('phrase').count()
-phrases = phrases.withColumnRenamed('count','phraseCount')
phrases = phrases.withColumn("phraseLogProb", f.log(f.col("phraseCount")) - logN)
-
# count term occurrances
phrases = phrases.withColumn('terms',f.split(f.col('phrase'),' '))
terms = phrases.select(['phrase','phraseCount','phraseLogProb',f.explode(phrases.terms).alias('term')])
df = terms.select(['phrase','phraseCount','phraseLogProb','phrasePWMI'])
-df = df.repartition('phrasePWMI')
df = df.sort(['phrasePWMI'],descending=True)
df = df.sortWithinPartitions(['phrasePWMI'],descending=True)
df.write.parquet("/gscratch/comdata/users/nathante/reddit_comment_ngrams_pwmi.parquet/",mode='overwrite',compression='snappy')
+
+df = spark.read.parquet("/gscratch/comdata/users/nathante/reddit_comment_ngrams_pwmi.parquet/")
+
df.write.csv("/gscratch/comdata/users/nathante/reddit_comment_ngrams_pwmi.csv/",mode='overwrite',compression='none')
+
+df = spark.read.parquet("/gscratch/comdata/users/nathante/reddit_comment_ngrams_pwmi.parquet")
+df = df.select('phrase','phraseCount','phraseLogProb','phrasePWMI')
+
+# choosing phrases occurring at least 3500 times in the 10% sample (35000 times) and then with a PWMI of at least 3 yeids about 65000 expressions.
+#
+df = df.filter(f.col('phraseCount') > 3500).filter(f.col("phrasePWMI")>3)
+df = df.toPandas()
+df.to_feather("/gscratch/comdata/users/nathante/reddit_multiword_expressions.feather")
+df.to_csv("/gscratch/comdata/users/nathante/reddit_multiword_expressions.csv")