[GitHub] [jena] rvesse commented on issue #568: Add Aggregate Median to SPARQL ARQ syntax

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rvesse commented on issue #568: Add Aggregate Median to SPARQL ARQ syntax
URL: https://github.com/apache/jena/pull/568#issuecomment-493031741
 
 
   One observation is that the Commons Math library used notes that for percentile based stats to be evaluated correctly the data should be at least partially ordered (http://commons.apache.org/proper/commons-math/javadocs/api-3.6/org/apache/commons/math3/stat/descriptive/rank/Percentile.html). Since aggregation is computed prior to sorting in SPARQL there’s no guarantee that the accumulator will see the data in a sensible order and thus calculate a meaningful result. 
   
   Could do with some test cases to see what happens in the case of generated random data inputs and may need some refactoring to do internal sorting of the accumulated values prior to passing them to the Math library

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