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https://issues.apache.org/jira/browse/SPARK-8375?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sean Owen resolved SPARK-8375.
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Resolution: Invalid
@sam This is a discussion for the mailing list rather than a JIRA.
https://cwiki.apache.org/confluence/display/SPARK/Contributing+to+Spark
You're looking at an API from 4 versions ago, too.
https://spark.apache.org/docs/1.4.0/api/scala/index.html#org.apache.spark.mllib.evaluation.BinaryClassificationMetrics
The input are scores and ground-truth labels. I agree with the problem of many
distinct values, but, this is part of the newer API.
> BinaryClassificationMetrics in ML Lib has odd API
> -------------------------------------------------
>
> Key: SPARK-8375
> URL: https://issues.apache.org/jira/browse/SPARK-8375
> Project: Spark
> Issue Type: Bug
> Components: MLlib
> Reporter: sam
>
> According to
> https://spark.apache.org/docs/1.0.0/api/scala/index.html#org.apache.spark.mllib.evaluation.BinaryClassificationMetrics
> The constructor takes `RDD[(Double, Double)]` which does not make sense it
> should be `RDD[(Double, T)]` or at least `RDD[(Double, Int)]`.
> In scikit I believe they use the number of unique scores to determine the
> number of thresholds and the ROC. I assume this is what
> BinaryClassificationMetrics is doing since it makes no mention of buckets.
> In a Big Data context this does not make sense as the number of unique scores
> may be huge.
> Rather user should be able to either specify the number of buckets, or the
> number of data points in each bucket. E.g. `def roc(numPtsPerBucket: Int)`
> Finally it would then be good if either the ROC output type was changed or
> another method was added that returned confusion matricies, so that the hard
> integer values can be obtained. E.g.
> ```
> case class Confusion(tp: Int, fp: Int, fn: Int, tn: Int) {
> // bunch of methods for each of the things in the table here
> https://en.wikipedia.org/wiki/Receiver_operating_characteristic
> }
> ...
> def confusions(numPtsPerBucket: Int): RDD[Confusion]
> ```
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