Carl Witt created MATH-1129:
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Summary: 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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