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https://issues.apache.org/jira/browse/MADLIB-1240?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Frank McQuillan closed MADLIB-1240.
-----------------------------------
Resolution: Fixed
> Vector to Columns
> -----------------
>
> Key: MADLIB-1240
> URL: https://issues.apache.org/jira/browse/MADLIB-1240
> Project: Apache MADlib
> Issue Type: New Feature
> Components: Module: Utilities
> Reporter: Frank McQuillan
> Assignee: Nandish Jayaram
> Priority: Major
> Fix For: v1.15
>
>
> related to https://issues.apache.org/jira/browse/MADLIB-1239
> Vector to Columns
> Converts a feature array in a single column of an output table into multiple
> columns. This process can be used to reverse the function cols2vec.
> {code}
> vec2cols(
> source_table,
> out_table,
> vector_col,
> feature_names,
> 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.
> vector_col
> TEXT. Name of the column containing the feature array. Must be a
> one-dimensional array.
> feature_names (optional)
> TEXT[]. Array of names associated with the feature array. Note that this
> array exists in the summary table created by the function 'cols2vec'. If the
> feature_names array is not specified, column names will be automatically
> generated of the form 'f1, f2, ...fn'
> 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 columns. To
> keep all columns from the source table, use '*'.
> Output
> The output table produced by the vec2cols function contains the following
> columns:
> <...>
> Columns from source table, depending on which ones are kept (if any).
> feature columns
> Columns for each of the features in 'vector_col'. Column type will depend on
> the feature array type in the source table. Column naming will depend on
> whether the parameter 'feature_names' is used.
> {code}
> Notes
> (1)
> The function
> http://pivotalsoftware.github.io/PDLTools/group__ArrayUtilities.html
> 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}
> vec2cols(
> table_name,
> output_table,
> vector_column,
> NULL,
> '*'
> )
> {code}
> (2)
> Please put the generated feature columns on the right side of the output
> table, i.e., they will be the last column on the right. Maintain the order
> of the array.
> Examples of feature name usage
> {code}
> select vec2cols(
> source_table,
> out_table,
> vector_col,
> SELECT col_names FROM a_table, -- feature name array exists in table
> 'a_table'
> cols_to_output
> )
> {code}
> OR
> {code}
> select vec2cols(
> source_table,
> out_table,
> vector_col,
> dictionary,
> cols_to_output
> ) from (select col_names as feature_names from a_table) q -- feature names
> array exists in table 'a_table'
> {code}
> OR
> {code}
> select vec2cols(
> source_table,
> out_table,
> vector_col,
> {'n1', 'n2'... 'nn'}, -- user explicitly enters feature names
> cols_to_output
> )
> {code}
> OR
> {code}
> select vec2cols(
> source_table,
> out_table,
> vector_col,
> NULL, -- no dictionary exists, will auto-generate column names as f1, f2, ...
> cols_to_output
> )
> {code}
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