[MATH-163] The evaluate method and the getResult method of class Variance give different results

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: 1.1
• Fix Version/s: 1.2
• Assignee: Unassigned
• Reporter: Nele Smeets
• Created: 29/Mar/07 14:25
• Updated: 23/Apr/09 02:26
• Resolved: 11/Jun/07 04:47

Description

Consider the following test code:

// construct an array of input values, containing infinity
double[] values = new double[]

{1.0, 2.0, Double.POSITIVE_INFINITY}

;
// find the variance using Variance.evaluate(double[])
Variance var1 = new Variance();
double value1 = var1.evaluate(values);
// find the variance using Variance.getResult()
Variance var2 = new Variance();
var2.incrementAll(values);
double value2 = var2.getResult();
// print out the results
System.out.println(value1);
System.out.println(value2);

This code prints out:

NaN
Infinity

So, we get two different variances, depending on the method we use.
(The same is true when we use Double.NEGATIVE_INFINITY as input value instead of Double.POSITIVE_INFINITY.)