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https://issues.apache.org/jira/browse/SPARK-22239?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Li Jin updated SPARK-22239:
---------------------------
    Description: 
Window function is another place we can benefit from vectored udf and add 
another useful function to the pandas_udf suite.

Example usage (preliminary):
{code:java}
w = Window.partitionBy('id').rowsBetween(Window.unbounedPreceding, 
Window.unbounedFollowing)

@pandas_udf(DoubleType())
def mean_udf(v):
    return v.mean()

df.withColumn('v_mean', mean_udf(df.v1).over(window))
{code}

  was:
Window function is another place we can benefit from vectored udf and add 
another useful function to the pandas_udf suite.

Example usage (preliminary):

{code:java}
w = Window.partitionBy('id').orderBy('time').rangeBetween(-200, 0)

@pandas_udf(DoubleType())
def ema(v1):
    return v1.ewm(alpha=0.5).mean().iloc[-1]

df.withColumn('v1_ema', ema(df.v1).over(window))
{code}




> User-defined window functions with pandas udf (unbounded window)
> ----------------------------------------------------------------
>
>                 Key: SPARK-22239
>                 URL: https://issues.apache.org/jira/browse/SPARK-22239
>             Project: Spark
>          Issue Type: Sub-task
>          Components: PySpark
>    Affects Versions: 2.2.0
>         Environment: 
>            Reporter: Li Jin
>            Assignee: Li Jin
>            Priority: Major
>             Fix For: 2.4.0
>
>
> Window function is another place we can benefit from vectored udf and add 
> another useful function to the pandas_udf suite.
> Example usage (preliminary):
> {code:java}
> w = Window.partitionBy('id').rowsBetween(Window.unbounedPreceding, 
> Window.unbounedFollowing)
> @pandas_udf(DoubleType())
> def mean_udf(v):
>     return v.mean()
> df.withColumn('v_mean', mean_udf(df.v1).over(window))
> {code}



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