[ARROW-14052] [C++] Add appx_median, hash_appx_median functions

• Type: Improvement
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: 6.0.0
• Component/s: C++
• Labels: kernel pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/29649
• Assignee: David Li
• Reporter: Ian Cook
• Created: 21/Sep/21 04:38
• Updated: 11/Jan/23 08:37
• Resolved: 24/Sep/21 13:01

Description

The Arrow C++ library has tdigest and hash_tdigest kernels that return arrays/lists. We call these from bindings with q = 0.5 to find the approximate median, but the output is difficult to work with. It would be nice to create kernels wrapping these that would produce scalar output per array/group:

appx_median --> tdigest(q = 0.5)

hash_appx_median --> hash_tdigest(q = 0.5)

Issue Links

• blocks: ARROW-13772 [R] Binding for median() and quantile() aggregation functions
• links to: GitHub Pull Request #11204