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https://issues.apache.org/jira/browse/SPARK-21900?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16151760#comment-16151760
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Jakob Bach commented on SPARK-21900:
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Ok, thanks, my fault, I did not expected something like e-17 at the end of the
truncated number, but I rather assumed that the whole result was a number
significantly greater than zero. Anyway, I suppose this "bug" can be closed.
> Numerical Error in simple Skewness Computation
> ----------------------------------------------
>
> Key: SPARK-21900
> URL: https://issues.apache.org/jira/browse/SPARK-21900
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.2.0
> Reporter: Jakob Bach
> Priority: Minor
>
> The skewness() aggregate SQL function in the Scala implementation
> (org.apache.spark.sql.skewness) seems to be buggy .The following code
> {code:java}
> import org.apache.spark.sql.functions
> import org.apache.spark.sql.SparkSession
> object SkewTest {
> def main(args: Array[String]): Unit = {
> val spark = SparkSession.
> builder().
> appName("Skewness example").
> master("local[1]").
> getOrCreate()
>
> spark.createDataFrame(Seq(4,1,2,3).map(Tuple1(_))).agg(functions.skewness("_1")).show()
> }
> }
> {code}
> should output 0 (as it does for Seq(1,2,3,4)), but outputs
> {code:none}
> +--------------------+
> | skewness(_1)|
> +--------------------+
> |5.958081967793454...|
> +--------------------+
> {code}
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