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Posted to issues@spark.apache.org by "Reynold Xin (JIRA)" <ji...@apache.org> on 2015/05/01 22:33:06 UTC
[jira] [Resolved] (SPARK-7240) Covariance for DataFrames
[ https://issues.apache.org/jira/browse/SPARK-7240?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Reynold Xin resolved SPARK-7240.
--------------------------------
Resolution: Fixed
Fix Version/s: 1.4.0
> Covariance for DataFrames
> -------------------------
>
> Key: SPARK-7240
> URL: https://issues.apache.org/jira/browse/SPARK-7240
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Reporter: Xiangrui Meng
> Assignee: Burak Yavuz
> Fix For: 1.4.0
>
>
> This JIRA is for computing stable covariance between two columns. The method `cov` should live under `df.stat` (similar to `na`).
> {code}
> df.stat.cov(col1, col2): Double
> {code}
> Stable algorithm: http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Covariance
> UDAF support will be added later. Then users can do
> {code}
> df.groupBy("gender").agg(cov("age", "salary").as("cov_age_salary"))
> {code}
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