GitHub user dongjoon-hyun opened a pull request: https://github.com/apache/spark/pull/13403
[SPARK-15660][CORE] RDD and Dataset should show the consistent values for variance/stdev. ## What changes were proposed in this pull request? In Spark-11490, `variance/stdev` are redefined as the **sample** `variance/stdev` instead of population ones. This PR addresses the only remaining legacy in RDD. This may cause breaking changes, but we had better be consistent in Spark 2.0 if possible. This PR also `popVariance` and `popStdev` functions. ```scala scala> val rdd = sc.parallelize(Seq(1.0, 2.0, 3.0)) rdd: org.apache.spark.rdd.RDD[Double] = ParallelCollectionRDD[0] at parallelize at <console>:24 scala> rdd.stdev res0: Double = 0.816496580927726 scala> rdd.toDS().describe().show() 16/05/30 22:20:12 WARN ObjectStore: Version information not found in metastore. hive.metastore.schema.verification is not enabled so recording the schema version 1.2.0 16/05/30 22:20:12 WARN ObjectStore: Failed to get database default, returning NoSuchObjectException +-------+-----+ |summary|value| +-------+-----+ | count| 3| | mean| 2.0| | stddev| 1.0| | min| 1.0| | max| 3.0| +-------+-----+ ``` ## How was this patch tested? Pass the updated Jenkins tests. You can merge this pull request into a Git repository by running: $ git pull https://github.com/dongjoon-hyun/spark SPARK-15660 Alternatively you can review and apply these changes as the patch at: https://github.com/apache/spark/pull/13403.patch To close this pull request, make a commit to your master/trunk branch with (at least) the following in the commit message: This closes #13403 ---- commit 3fe0cb6024ba44b1645bc74f1fbe29267571caa0 Author: Dongjoon Hyun <dongj...@apache.org> Date: 2016-05-31T05:22:16Z [SPARK-15660][CORE] RDD and Dataset should show the consistent value for variance/stdev. ---- --- If your project is set up for it, you can reply to this email and have your reply appear on GitHub as well. If your project does not have this feature enabled and wishes so, or if the feature is enabled but not working, please contact infrastructure at infrastruct...@apache.org or file a JIRA ticket with INFRA. --- --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org