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From "Sean Owen (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (SPARK-23091) Incorrect unit test for approxQuantile
Date Tue, 16 Jan 2018 19:36:01 GMT

     [ https://issues.apache.org/jira/browse/SPARK-23091?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sean Owen updated SPARK-23091:
------------------------------
    Environment:     (was: Agree, go ahead with a PR.)

Agree, go ahead with a PR.

> Incorrect unit test for approxQuantile
> --------------------------------------
>
>                 Key: SPARK-23091
>                 URL: https://issues.apache.org/jira/browse/SPARK-23091
>             Project: Spark
>          Issue Type: Improvement
>          Components: ML, Tests
>    Affects Versions: 2.2.1
>            Reporter: Kuang Chen
>            Priority: Minor
>
> Currently, test for `approxQuantile` (quantile estimation algorithm) checks whether
estimated quantile is within +- 2*`relativeError` from the true quantile. See the code below:
> [https://github.com/apache/spark/blob/master/sql/core/src/test/scala/org/apache/spark/sql/DataFrameStatSuite.scala#L157]
> However, based on the original paper by Greenwald and Khanna, the estimated quantile
is guaranteed to be within +- `relativeError` from the true quantile. Using the double "tolerance"
is misleading and incorrect, and we should fix it.
>  



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