[jira] [Resolved] (SPARK-13641) getModelFeatures of ml.api.r.SparkRWrapper cannot (always) reveal the original column names

["Hyukjin Kwon (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-13641?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hyukjin Kwon resolved SPARK-13641.
----------------------------------
    Resolution: Incomplete

> getModelFeatures of ml.api.r.SparkRWrapper cannot (always) reveal the original column names
> -------------------------------------------------------------------------------------------
>
>                 Key: SPARK-13641
>                 URL: https://issues.apache.org/jira/browse/SPARK-13641
>             Project: Spark
>          Issue Type: Bug
>          Components: ML, SparkR
>            Reporter: Xusen Yin
>            Priority: Minor
>              Labels: bulk-closed
>
> getModelFeatures of ml.api.r.SparkRWrapper cannot (always) reveal the original column names. Let's take the HouseVotes84 data set as an example:
> {code}
> case m: XXXModel =>
>   val attrs = AttributeGroup.fromStructField(
>     m.summary.predictions.schema(m.summary.featuresCol))
>   attrs.attributes.get.map(_.name.get)
> {code}
> The code above gets features' names from the features column. Usually, the features column is generated by RFormula. The latter has a VectorAssembler in it, which leads the output attributes not equal with the original ones.
> E.g., we want to learn the HouseVotes84's features' name "V1, V2, ..., V16". But with RFormula, we can only get "V1_n, V2_y, ..., V16_y" because [the transform function of VectorAssembler|https://github.com/apache/spark/blob/master/mllib/src/main/scala/org/apache/spark/ml/feature/VectorAssembler.scala#L75] adds salts of the column names.



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