Counter function on a ArrayColumn Pyspark

Question

From this data frame

+-----+-----------------+ |store| values | +-----+-----------------+ | 1|[1, 2, 3,4, 5, 6]| | 2| [2,3]| +-----+-----------------+

I would like to apply the Counter function to get this:

+-----+------------------------------+ |store| values | +-----+------------------------------+ | 1|{1:1, 2:1, 3:1, 4:1, 5:1, 6:1}| | 2|{2:1, 3:1} | +-----+------------------------------+

I got this data frame using the answer of another question :

GroupBy and concat array columns pyspark

So I try to modify the code that is in the answers like this:

Option 1:

def flatten_counter(val): return Counter(reduce (lambda x, y:x+y, val)) udf_flatten_counter = sf.udf(flatten_counter, ty.ArrayType(ty.IntegerType())) df3 = df2.select("store", flatten_counter("values2").alias("values3")) df3.show(truncate=False)

Option 2:

df.rdd.map(lambda r: (r.store, r.values)).reduceByKey(lambda x, y: x + y).map(lambda row: Counter(row[1])).toDF(['store', 'values']).show()

but it doesn't work.

Does anybody know how can I do it?

Thank you

Alper t. Turker · Accepted Answer · 2018-01-24 16:34:16Z

You just have to provide correct data type

udf_flatten_counter = sf.udf( lambda x: dict(Counter(x)), ty.MapType(ty.IntegerType(), ty.IntegerType())) df = spark.createDataFrame( [(1, [1, 2, 3, 4, 5, 6]), (2, [2, 3])], ("store", "values")) df.withColumn("cnt", udf_flatten_counter("values")).show(2, False) # +-----+------------------+---------------------------------------------------+ # |store|values |cnt | # +-----+------------------+---------------------------------------------------+ # |1 |[1, 2, 3, 4, 5, 6]|Map(5 -> 1, 1 -> 1, 6 -> 1, 2 -> 1, 3 -> 1, 4 -> 1)| # |2 |[2, 3] |Map(2 -> 1, 3 -> 1) | # +-----+------------------+---------------------------------------------------+

Similarly with RDD

df.rdd.mapValues(Counter).mapValues(dict).toDF(["store", "values"]).show(2, False) # +-----+---------------------------------------------------+ # |store|values | # +-----+---------------------------------------------------+ # |1 |Map(5 -> 1, 1 -> 1, 6 -> 1, 2 -> 1, 3 -> 1, 4 -> 1)| # |2 |Map(2 -> 1, 3 -> 1) | # +-----+---------------------------------------------------+

Conversion to dict is necessary because apparently Pyrolite cannot handle Counter objects.

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