How do you Convert VectorUDTs into Columns in PySpark?

Unraveling VectorUDTs into Columns Using PySpark

In PySpark, you may encounter the need to extract individual dimensions from vector columns stored as VectorUDTs. To accomplish this, you can leverage various approaches based on your Spark version.

Spark >= 3.0.0

PySpark 3.0.0 brings built-in functionality for this task:

<code class="python">from pyspark.ml.functions import vector_to_array

df.withColumn("xs", vector_to_array("vector")).select(["word"] + [col("xs")[i] for i in range(3)])</code>

This concisely converts the vector into an array and projects the desired columns.

Spark

Pre-3.0.0 Spark versions require more intricate approaches:

RDD Conversion:

<code class="python">df.rdd.map(lambda row: (row.word,) + tuple(row.vector.toArray().tolist())).toDF(["word"])</code>

UDF Method:

<code class="python">from pyspark.sql.functions import udf, col
from pyspark.sql.types import ArrayType, DoubleType

def to_array(col):
    return udf(lambda v: v.toArray().tolist(), ArrayType(DoubleType()))(col)

df.withColumn("xs", to_array(col("vector"))).select(["word"] + [col("xs")[i] for i in range(3)])</code>

Note: For increased performance, ensure asNondeterministic is used with the UDF (requires Spark 2.3 ).

Scala Equivalent

For the Scala equivalent of these approaches, refer to "Spark Scala: How to convert Dataframe[vector] to DataFrame[f1:Double, ..., fn: Double)]."

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