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https://issues.apache.org/jira/browse/MATH-1129?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14035524#comment-14035524
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Gilles commented on MATH-1129:
------------------------------

bq. [...] so I'd rather like to stay out of development issues.

Development is also driven by user needs.

If you are satisfied with the current status of this issue, I'm fine to leave 
it at that. Thanks for the report.


> Percentile Computation errs
> ---------------------------
>
>                 Key: MATH-1129
>                 URL: https://issues.apache.org/jira/browse/MATH-1129
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 3.2
>         Environment: Java 1.8.0
>            Reporter: Carl Witt
>
> In the following test, the 75th percentile is _smaller_ than the 25th 
> percentile, leaving me with a negative interquartile range.
> {code:title=Bar.java|borderStyle=solid}
> @Test public void negativePercentiles(){
>         double[] data = new double[]{
>                 -0.012086732064244697, 
>                 -0.24975668704012527, 
>                 0.5706168483164684, 
>                 -0.322111769955327, 
>                 0.24166759508327315, 
>                 Double.NaN, 
>                 0.16698443218942854, 
>                 -0.10427763937565114, 
>                 -0.15595963093172435, 
>                 -0.028075857595882995, 
>                 -0.24137994506058857, 
>                 0.47543170476574426, 
>                 -0.07495595384947631, 
>                 0.37445697625436497, 
>                 -0.09944199541668033
>         };
>         DescriptiveStatistics descriptiveStatistics = new 
> DescriptiveStatistics(data);
>         double threeQuarters = descriptiveStatistics.getPercentile(75);
>         double oneQuarter = descriptiveStatistics.getPercentile(25);
>         double IQR = threeQuarters - oneQuarter;
>         
>         System.out.println(String.format("25th percentile %s 75th percentile 
> %s", oneQuarter, threeQuarters ));
>         
>         assert IQR >= 0;
>         
>     }
> {code}



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