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https://issues.apache.org/jira/browse/SPARK-6548?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14639914#comment-14639914
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Yin Huai commented on SPARK-6548:
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[~JihongMA] Will you have time to implement stddev based on our new aggregate
function interface? {{AlgebraicAggregate}} is the abstract class to use and you
can take a look at
{{org.apache.spark.sql.catalyst.expressions.aggregate.Average}} as an example.
Let me know if you have any question. Thanks!
> stddev_pop and stddev_samp aggregate functions
> ----------------------------------------------
>
> Key: SPARK-6548
> URL: https://issues.apache.org/jira/browse/SPARK-6548
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Reporter: Reynold Xin
> Labels: DataFrame, starter
>
> Add it to the list of aggregate functions:
> https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
> Also add it to
> https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/GroupedData.scala
> We can either add a Stddev Catalyst expression, or just compute it using
> existing functions like here:
> https://github.com/apache/spark/commit/5bbcd1304cfebba31ec6857a80d3825a40d02e83#diff-c3d0394b2fc08fb2842ff0362a5ac6c9R776
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