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 <[email protected]>
Date: 2016-05-31T05:22:16Z
[SPARK-15660][CORE] RDD and Dataset should show the consistent value for
variance/stdev.
----
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