[jira] [Commented] (MADLIB-1239) Columns to Vector

["Frank McQuillan (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MADLIB-1239?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16498641#comment-16498641 ] 

Frank McQuillan commented on MADLIB-1239:
-----------------------------------------

[~hpandey]



(1)
If cols_to_output = NULL (default), it means to only output the feature vector, and no other columns from the source_table.  If the user wants out_table contain all the source table columns + feature vector, they should specify '*' for the parameter cols_to_output.  If they only want columns 'a' and 'b' to be output along with the feature vector, they would say cols_to_output = 'a, b'

See sessionize for an example
http://madlib.apache.org/docs/latest/group__grp__sessionize.html


(2) 
The parameter list_of_features_to_exclude only makes sense when list_of_features = '*'.
For example if you say:

list_of_features = '*'
list_of_features_to_exclude = 'x, y, z'

it means use all of the columns from the source table for features, except for x, y, z

See decision tree for an example
http://madlib.apache.org/docs/latest/group__grp__decision__tree.html


Also, please ensure that you handle special characters and UTF-8 in the usual way.

Also, please ensure to maintain column order.




> Columns to Vector
> -----------------
>
>                 Key: MADLIB-1239
>                 URL: https://issues.apache.org/jira/browse/MADLIB-1239
>             Project: Apache MADlib
>          Issue Type: New Feature
>          Components: Module: Utilities
>            Reporter: Frank McQuillan
>            Assignee: Himanshu Pandey
>            Priority: Major
>             Fix For: v1.15
>
>
> related to https://issues.apache.org/jira/browse/MADLIB-1240
> Columns to Vector
> Converts features from multiple columns of an input table into a feature array in a single column.
> This process can be reversed using the function vec2cols.
> {code}
> cols2vec(
>     source_table,
>     out_table,
>     list_of_features,
>     list_of_features_to_exclude,
>     cols_to_output
>     )
> source_table
> TEXT. Name of the table containing the source data.
> out_table
> TEXT. Name of the generated table containing the output. If a table with the same name already exists, an error will be returned. 
> list_of_features
> TEXT. Comma-separated string of column names or expressions to put into feature array. Can also be a '*' implying all columns are to be put into feature array (except for the ones included in the next argument that lists exclusions). Array columns in the source table are not supported in the 'list_of_features'.
> PostgreSQL arrays only allow elements of the same type.  If multiple numeric types are present in the 'list_of_features', they will be cast to the largest type.  For example, if there are INTEGER and DOUBLE PRECISION columns in the feature list, the feature array will be of type DOUBLE PRECISION[].  Invalid combinations like TEXT and INTEGER will result in an error.
> list_of_features_to_exclude (optional)
> TEXT, default NULL. Comma-separated string of column names to exclude from the feature array.  Use only when 'list_of_features' is '*'.
> cols_to_output (optional)
> TEXT, default NULL. Comma-separated string of column names from the source table to keep in the output table, in addition to the feature array.  To keep all columns from the source table, use '*'.
> Output
> The output table produced by the cols2vec function contains the following columns:
> <...>
> Columns from source table, depending on which ones are kept (if any).
> feature_vector
> Array of features.  Array type will depend on feature type in the source table.
> A summary table named <out_table>_summary is also created at the same time, which lists the names of the features.
> feature_names
> TEXT[] Array of names of features.
> {code}
> Notes
> (1)
> The function
> http://pivotalsoftware.github.io/PDLTools/group__grp__array__utilities.html#cols2vec_example
> is similar but the proposed MADlib one has more options.  To do the equivalent of the PDL Tools one in MADlib, you would do:
> {code}
> cols2vec(
>     table_name,
>     output_table,
>     '*',
>     exclude_columns,
>     '*',
>     )
> {code}
> (2)
> Please put the feature vector on the right side of the output table, i.e., it will be the last column on the right.



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