spark-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Dongjoon Hyun (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (SPARK-15660) RDD and Dataset should show the consistent value for variance/stdev.
Date Tue, 31 May 2016 09:52:12 GMT

     [ https://issues.apache.org/jira/browse/SPARK-15660?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Dongjoon Hyun updated SPARK-15660:
----------------------------------
    Description: 
In Spark-11490, `variance/stdev` are redefined as the **sample** `variance/stdev` instead
of population ones.

This issue addresses the only remaining legacy in RDD. This may cause breaking changes, but
we had better be consistent in Spark 2.0 if possible.
{code}
scala> val ds = spark.createDataset(Seq(1.0, 2.0, 3.0))
ds: org.apache.spark.sql.Dataset[Double] = [value: double]

scala> ds.describe().show()
+-------+-----+                                                                 
|summary|value|
+-------+-----+
|  count|    3|
|   mean|  2.0|
| stddev|  1.0|
|    min|  1.0|
|    max|  3.0|
+-------+-----+

scala> ds.rdd.stdev
res1: Double = 0.816496580927726
{code}

  was:
In Spark-11490, `variance/stdev` are redefined as the **sample** `variance/stdev` instead
of population ones.

This issue addresses the only remaining legacy in RDD. This may cause breaking changes, but
we had better be consistent in Spark 2.0 if possible.
{code}
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|
+-------+-----+
{code}


> RDD and Dataset should show the consistent value for variance/stdev.
> --------------------------------------------------------------------
>
>                 Key: SPARK-15660
>                 URL: https://issues.apache.org/jira/browse/SPARK-15660
>             Project: Spark
>          Issue Type: Bug
>          Components: Spark Core
>            Reporter: Dongjoon Hyun
>
> In Spark-11490, `variance/stdev` are redefined as the **sample** `variance/stdev` instead
of population ones.
> This issue addresses the only remaining legacy in RDD. This may cause breaking changes,
but we had better be consistent in Spark 2.0 if possible.
> {code}
> scala> val ds = spark.createDataset(Seq(1.0, 2.0, 3.0))
> ds: org.apache.spark.sql.Dataset[Double] = [value: double]
> scala> ds.describe().show()
> +-------+-----+                                                                 
> |summary|value|
> +-------+-----+
> |  count|    3|
> |   mean|  2.0|
> | stddev|  1.0|
> |    min|  1.0|
> |    max|  3.0|
> +-------+-----+
> scala> ds.rdd.stdev
> res1: Double = 0.816496580927726
> {code}



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscribe@spark.apache.org
For additional commands, e-mail: issues-help@spark.apache.org


Mime
View raw message