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https://issues.apache.org/jira/browse/HIVE-1397?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12879177#action_12879177
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John Sichi commented on HIVE-1397:
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+1. Will commit if tests pass.
> histogram() UDAF for a numerical column
> ---------------------------------------
>
> Key: HIVE-1397
> URL: https://issues.apache.org/jira/browse/HIVE-1397
> Project: Hadoop Hive
> Issue Type: New Feature
> Components: Query Processor
> Affects Versions: 0.6.0
> Reporter: Mayank Lahiri
> Assignee: Mayank Lahiri
> Fix For: 0.6.0
>
> Attachments: Histogram_quality.png.jpg, HIVE-1397.1.patch,
> HIVE-1397.2.patch
>
>
> A histogram() UDAF to generate an approximate histogram of a numerical (byte,
> short, double, long, etc.) column. The result is returned as a map of (x,y)
> histogram pairs, and can be plotted in Gnuplot using impulses (for example).
> The algorithm is currently adapted from "A streaming parallel decision tree
> algorithm" by Ben-Haim and Tom-Tov, JMLR 11 (2010), and uses space
> proportional to the number of histogram bins specified. It has no
> approximation guarantees, but seems to work well when there is a lot of data
> and a large number (e.g. 50-100) of histogram bins specified.
> A typical call might be:
> SELECT histogram(val, 10) FROM some_table;
> where the result would be a histogram with 10 bins, returned as a Hive map
> object.
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