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From "Guha, Rajarshi (NIH/NCATS) [C]" <gu...@mail.nih.gov>
Subject [math] hypergeometric distribution giving incorrect results
Date Tue, 04 Sep 2012 02:14:02 GMT
Hi, I'm using  commons math 2.2 and the values from the hypergeometric distribution do not
seem to match an alternative implementation (from R 2.15.1). The code I'm using is

        HypergeometricDistributionImpl d = 
		new HypergeometricDistributionImpl(2550, 61, 8);
        double logp = Math.log(1 - d.cumulativeProbability(7));

Using JDK 1.6.1, logp comes out to be -30.258290927468533

However, on R 2.15.1 when doing 

	phyper(7, 61, 2489, 8, lower=F, log.p=T)

I get -30.33188

This seems to be a pretty big difference and in the project that I'm using commons-math prevents
me from porting some R code to Java.

Can anybody confirm these results? Is this a bug? Or am I invoking something in the wrong
way?

Pointers would be appreciated.
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