[MATH-1495] Calling NaturalRanking#rank() on an array of all NaNs throws a misleading ArrayIndexOutOfBoundsException when the NanStrategy is REMOVED

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Assignee: Unassigned
• Reporter: Akash Srivastava
• Created: 09/Aug/19 06:53
• Updated: 14/Aug/19 10:18

Description

Consider the following code:

import org.apache.commons.math3.stat.ranking.NaNStrategy;
import org.apache.commons.math3.stat.ranking.NaturalRanking;
import org.apache.commons.math3.stat.ranking.TiesStrategy;
class AllNaNException{
public NaturalRanking naturalranking;
    public double[] AllNaNArray(){
    naturalranking = new NaturalRanking(NaNStrategy.REMOVED, TiesStrategy.AVERAGE);
        double[] x = {Double.NaN, Double.NaN};
        double[] y = naturalranking.rank(x);
        return y;
    }
    public static void main(String[] args) {
        AllNaNException a = new AllNaNException();
        double[] res = a.bug();
        System.out.println(res[0] + "," + res[1]);
    }

}

Compiled it by: javac -cp /usr/share/java/commons-math3-3.6.1.jar tryit.java

Executed it by: java -cp /usr/share/java/commons-math3-3.6.1.jar:. tryit

 

Output:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
at org.apache.commons.math3.stat.ranking.NaturalRanking.rank(NaturalRanking.java:231)
at tryit.bug(tryit.java:9)
at tryit.main(tryit.java:14)

 

Currently, calling NaturalRanking#rank() on an array of all NaNs throws a misleading ArrayIndexOutOfBoundsException when the NanStrategy is REMOVED. I am unsure what outcome the user should expect in code like the test case I have provided below. Can you shed some light on this? I am happy to write a pull request once I know what fix would be best. I think throwing an IllegalArgumentException or returning an empty array would be more apt in this case.