Hello, I'm working on adding Standard Deviation and others to the list of Aggregations, https://issues.apache.org/jira/browse/FLINK-3613
Unfortunately, I didn't get very far because the general design of Aggreation on DataSets needs to change and each solution seems to have drawbacks. For example, one easy solution would be to modify AggregateOperator to extend CustomUnaryOperation but that seems weird because then it wouldn't be an Operator. I wrote a design explaining some of the current limitations and background, https://issues.apache.org/jira/secure/attachment/12794820/DataSet-Aggregation-Design-March2016-v1.txt The design is in progress. I wanted to check in with people before going much further. I'd appreciate any feedback. Thanks, Todd
