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Posted to issues@spark.apache.org by "Sean Owen (JIRA)" <ji...@apache.org> on 2019/02/06 16:53:00 UTC
[jira] [Updated] (SPARK-26351) Documented formula of precision at k
does not match the actual code
[ https://issues.apache.org/jira/browse/SPARK-26351?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Sean Owen updated SPARK-26351:
------------------------------
Fix Version/s: (was: 2.3.4)
2.3.3
> Documented formula of precision at k does not match the actual code
> -------------------------------------------------------------------
>
> Key: SPARK-26351
> URL: https://issues.apache.org/jira/browse/SPARK-26351
> Project: Spark
> Issue Type: Bug
> Components: Documentation, MLlib
> Affects Versions: 2.4.0
> Reporter: Pablo J. Villacorta
> Assignee: shahid
> Priority: Minor
> Fix For: 2.3.3, 2.4.1, 3.0.0
>
>
> The formula of the *precision @ k* for measuring the quality of the recommendations:
> [https://spark.apache.org/docs/latest/mllib-evaluation-metrics.html#ranking-systems]
> says that j goes from 0 to *min(|D|, k)* , but according to the code,
> [https://github.com/apache/spark/blob/a63e7b2a212bab94d080b00cf1c5f397800a276a/mllib/src/main/scala/org/apache/spark/mllib/evaluation/RankingMetrics.scala#L65]
>
> {code:java}
> val n = math.min(pred.length, k){code}
>
> The notation of Spark documentation defines
> D_i as the set of ground truth relevant documents for user i
> R_i as the set of recommended documents (i.e. predictions) given for user i .
> According to the code, the documentation should say j goes from 0 to *min( | R_i |, k )*
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