[GitHub] spark pull request #17967: [SPARK-14659][ML] RFormula consistent with R when...

[HyukjinKwon]

Github user HyukjinKwon commented on a diff in the pull request:

    https://github.com/apache/spark/pull/17967#discussion_r117602143
  
    --- Diff: mllib/src/main/scala/org/apache/spark/ml/feature/RFormula.scala 
---
    @@ -38,29 +38,35 @@ import org.apache.spark.sql.types._
     private[feature] trait RFormulaBase extends HasFeaturesCol with 
HasLabelCol {
     
       /**
    -   * Param for how to order labels of string column. The first label after 
ordering is assigned
    -   * an index of 0.
    -   * Options are:
    -   *   - 'frequencyDesc': descending order by label frequency (most 
frequent label assigned 0)
    -   *   - 'frequencyAsc': ascending order by label frequency (least 
frequent label assigned 0)
    -   *   - 'alphabetDesc': descending alphabetical order
    -   *   - 'alphabetAsc': ascending alphabetical order
    -   * Default is 'frequencyDesc'.
    -   * When the ordering is set to 'alphabetDesc', `RFormula` drops the same 
category as R
    -   * when encoding strings.
    +   * Param for how to order categories of a FEATURE string column used by 
`StringIndexer`.
    +   * The last category after ordering is dropped when encoding strings.
    +   * The options are explained using an example string: 'b', 'a', 'b', 
'a', 'c', 'b'
    +   * |
    +   * | Option | Category mapped to 0 by StringIndexer |  Category dropped 
by RFormula
    --- End diff --
    
    Hm, up to my knowledge, it looks not. I guess @actuaryzhang meant to just 
write these out as they are? Let me double check by myself ....
    
    Scaladoc
    
    <img width="952" alt="2017-05-20 1 40 35" 
src="https://cloud.githubusercontent.com/assets/6477701/26273032/0d97fd84-3d62-11e7-8f18-1c89f539b1ae.png";>
    
    
    Javadoc
    
    <img width="1086" alt="2017-05-20 1 40 53" 
src="https://cloud.githubusercontent.com/assets/6477701/26273031/0bac57cc-3d62-11e7-8875-6f897b093633.png";>
    



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