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From "Zhihong Yu (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-5142) Compute standard deviation using AggregateProtocol
Date Mon, 09 Jan 2012 00:33:39 GMT

     [ https://issues.apache.org/jira/browse/HBASE-5142?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Zhihong Yu updated HBASE-5142:
------------------------------

    Comment: was deleted

(was: AggregationClient.std() already provides this capability.)
    
> Compute standard deviation using AggregateProtocol
> --------------------------------------------------
>
>                 Key: HBASE-5142
>                 URL: https://issues.apache.org/jira/browse/HBASE-5142
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Zhihong Yu
>
> Looking at http://en.wikipedia.org/wiki/Standard_deviation, I think two passes are involved
in computing std:
> 1. compute average, u
> 2. tuple of (sum of (xi-u)*(xi-u), number of rows) is returned from each region
> 3. client computes std based on results from step 2

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