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https://issues.apache.org/jira/browse/FLINK-3613?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15201538#comment-15201538
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Todd Lisonbee commented on FLINK-3613:
--------------------------------------

Sure, I'll create a design for this.  Thanks.

> Add standard deviation, mean, variance to list of Aggregations
> --------------------------------------------------------------
>
>                 Key: FLINK-3613
>                 URL: https://issues.apache.org/jira/browse/FLINK-3613
>             Project: Flink
>          Issue Type: Improvement
>            Reporter: Todd Lisonbee
>            Priority: Minor
>
> Implement standard deviation, mean, variance for 
> org.apache.flink.api.java.aggregation.Aggregations
> Ideally implementation should be single pass and numerically stable.
> References:
> "Scalable and Numerically Stable Descriptive Statistics in SystemML", Tian et 
> al, International Conference on Data Engineering 2012
> http://dl.acm.org/citation.cfm?id=2310392
> "The Kahan summation algorithm (also known as compensated summation) reduces 
> the numerical errors that occur when adding a sequence of finite precision 
> floating point numbers. Numerical errors arise due to truncation and 
> rounding. These errors can lead to numerical instability when calculating 
> variance."
> https://en.wikipedia.org/wiki/Kahan_summation_algorithm



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