[jira] [Resolved] (ARROW-81) [Format] Add a Category logical type (distinct from dictionary-encoding)

["Wes McKinney (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-81?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Wes McKinney resolved ARROW-81.
-------------------------------
    Resolution: Fixed

Issue resolved by pull request 297
[https://github.com/apache/arrow/pull/297]

> [Format] Add a Category logical type (distinct from dictionary-encoding)
> ------------------------------------------------------------------------
>
>                 Key: ARROW-81
>                 URL: https://issues.apache.org/jira/browse/ARROW-81
>             Project: Apache Arrow
>          Issue Type: New Feature
>          Components: C++
>            Reporter: Wes McKinney
>            Assignee: Wes McKinney
>
> A Category (or "factor") is a dictionary-encoded array whose dictionary has semantic meaning. The data consists of
> - An array of integer "codes"
> - A child array of some other type, known as the "categories" or "levels" of the array. Typically there is an "ordered" boolean flag indicating whether the order of the categories is meaningful.
> Category/factor types are used in a number of common statistical analyses. See, for example, http://www.voteview.com/R_Ordered_Logistic_or_Probit_Regression.htm. It is a basic requirement for Python and R, at least, as Arrow C++ consumers, to have this type. Separately, we should consider what is necessary to be able to transmit category data in IPCs -- possible an expansion of the Arrow format. 



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