Index String
===========

Maps a column of indices back to a new column of corresponding string values. The index-string mapping is either from the ML attributes of the input column, or from user-supplied labels

Type
--------- 

ml-transformer

Class
--------- 

fire.nodes.ml.NodeIndexString

Fields
--------- 

.. list-table::
      :widths: 10 5 10
      :header-rows: 1

      * - Name
        - Title
        - Description
      * - inputCol
        - Input Column
        - Column containing label indices
      * - outputCol
        - Output Column
        - Output column name


Details
-------
Index String Node Details
+++++++++++++++


An Index String Node is a Transformer that maps a column of indices back to a new column of corresponding string values. The index-string mapping is either from the ML attributes of the input column, or from user-supplied labels (which take precedence over ML attributes).

A common use case is to produce indices from labels with StringIndexer, train a model with those indices and retrieve the original labels from the column of predicted indices with IndexToString.



Input Parameters
+++++++++++++++


* OUTPUT STORAGE LEVEL : Keep this as DEFAULT.
* INPUT COLUMN : Select the column of label indices which needs to be transformed to its original category.
* OUTPUT COLUMN : A name for the output column which will contain the original label after transformation.


Examples
-------
Index String Node Example
+++++++++++++++


Consider the below datafrme which contains the transformed string column 'category' to indexed column 'categoryIndex'


::

    ----------------------------
    | id|category|categoryIndex|
    ----------------------------
    |  0|       a|          0.0|
    |  1|       b|          2.0|
    |  2|       c|          1.0|
    |  3|       a|          0.0|
    |  4|       a|          0.0|
    |  5|       c|          1.0|
    ----------------------------


On applying the **Index String Node** to the input column of **categoryIndex** we get the original string column **originalCategory**.


::

    ------------------------------------
    | id|categoryIndex|originalCategory|
    ------------------------------------
    |  0|          0.0|               a|
    |  1|          2.0|               b|
    |  2|          1.0|               c|
    |  3|          0.0|               a|
    |  4|          0.0|               a|
    |  5|          1.0|               c|
    ------------------------------------