[SOLR-13391] Add variance and standard deviation stream evaluators

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Resolved
• Fix Version/s: 8.1
• Component/s: streaming expressions
• Labels: pull-request-available
• Assignee: Joel Bernstein
• Reporter: Nazerke Seidan
• Created: 10/Apr/19 18:12
• Updated: 17/Jul/20 01:39
• Resolved: 12/Apr/19 14:09

Description

It seems variance and standard deviation stream evaluators are not supported by any of the solr version. For example, 

              let(echo="m,v,sd", arr=array(1,3,3), m=mean(a), v=var(a), sd=stddev(a))

So far, only the mean function is implemented. I think it is useful to have var and sttdev functions separately as a stream evaluator. 

Issue Links

• is duplicated by: SOLR-10682 Add variance Stream Evaluator
• is related to: SOLR-10651 Streaming Expressions statistical functions library
• links to: GitHub Pull Request #643