From maechler at stat.math.ethz.ch  Thu Nov 25 09:45:14 2004
From: maechler at stat.math.ethz.ch (maechler@stat.math.ethz.ch)
Date: Thu Nov 25 09:45:26 2004
Subject: (PR#7393) Re: [Rd] dhyper() does not allow non-integer values for
Message-ID: <20041125084514.AC365104CF@slim.kubism.ku.dk>

>>>>> "PD" == Peter Dalgaard <p.dalgaard@biostat.ku.dk>
>>>>>     on 24 Nov 2004 18:32:15 +0100 writes:

    PD> tlumley@u.washington.edu writes:
    >> > > dhyper() does not allow non-integer values for input
    >> parameters m and n.
    >> >
    >> > this is in contrast to the other functions in the
    >> _hyper() "family",
    >> 
    >> I would argue that the bug was in the other functions. If
    >> not, there is a= =20 bug in the documentation, which
    >> gives no way to tell what the result=20 should mean for
    >> non-integer m, n, k.


    PD> My initial reaction too (and surely it is not a bug that
    PD> functions behave inconsistently in regions where they
    PD> are not documented to work at all), but on the other
    PD> hand, noninteger m,n do appear to give a well-defined
    PD> distribution, and perhaps there's a way of making sense
    PD> of it? I wouldn't think it corresponds to noncentral
    PD> hypergeometric distributions.

I'd tend to pretty much agree here.

Incidentally (slightly related, but prompted by something completely different),
just these hours I've been extending
     choose(r, k)
to work not just for integer but all positive 'n'.

Martin


(PR#7393) Re: [Rd] dhyper() does not allow non-integer values for
maechler@stat.math.ethz.ch