[MATH-1129] Percentile Computation errs

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.2
• Fix Version/s: 3.4

Environment

Java 1.8.0

• Assignee: Unassigned
• Reporter: Carl Witt
• Created: 17/Jun/14 09:22
• Updated: 26/Dec/14 19:50
• Resolved: 05/Oct/14 18:44

Description

In the following test, the 75th percentile is smaller than the 25th percentile, leaving me with a negative interquartile range.

Bar.java

@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;
        
    }