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https://issues.apache.org/jira/browse/MATH-1146?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gilles updated MATH-1146:
-------------------------
Attachment: MATH-1146.patch
Here is a tentative patch which I thought would solve the problem.
However, it makes another unit test fail.
{noformat}
Tests run: 5, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec <<<
FAILURE! - in
org.apache.commons.math3.stat.descriptive.AggregateSummaryStatisticsTest
testAggregateSpecialValues(org.apache.commons.math3.stat.descriptive.AggregateSummaryStatisticsTest)
Time elapsed: 0.001 sec <<< FAILURE!
java.lang.AssertionError: expected:<Infinity> but was:<NaN>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:494)
at org.apache.commons.math3.TestUtils.assertEquals(TestUtils.java:55)
at
org.apache.commons.math3.stat.descriptive.AggregateSummaryStatisticsTest.assertEquals(AggregateSummaryStatisticsTest.java:236)
at
org.apache.commons.math3.stat.descriptive.AggregateSummaryStatisticsTest.testAggregateSpecialValues(AggregateSummaryStatisticsTest.java:222)
{noformat}
> class Mean returns incorrect result after processing an Infinity value
> ----------------------------------------------------------------------
>
> Key: MATH-1146
> URL: https://issues.apache.org/jira/browse/MATH-1146
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: 3.3
> Reporter: david cogen
> Attachments: MATH-1146.patch
>
>
> 1. Create a Mean object.
> 2. call increment() with Double.POSITIVE_INFINITY.
> 3. Call getResult(). Result is INFINITY as expected.
> 4. call increment() with 0.
> 5. Call getResult(). Result is NaN; not INFINITY as expected.
> This is apparently due to the "optimization" for calculating mean described
> in the javadoc. Rather than accumulating a sum, it maintains a running mean
> value using the formula "m = m + (new value - m) / (number of observations)",
> which unlike the "definition way", fails after an infinity.
> I was using Mean within a SummaryStatistics. Other statistics also seem to be
> affected; for example, the standard deviation also incorrectly gives NaN
> rather than Infinity. I don't know if that's due to the error in Mean or if
> the other stats classes have similar bugs.
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