R devel - Dec 2009 - qpois errors for degenerate distribution (PR#14135)

Full_Name: Jerry W. Lewis
Version: 2.10.0
OS: XP Professional
Submission from: (NULL) (96.237.55.233)


For a degenerate Poisson distribution (lambda==0), qpois(p,0,lower.tail) should
return 0 for any valid p, but qpois(1,0) and qpois(0,0,F) incorrectly return
Inf.

>>>>> "JL" == Jerry Lewis <Jerry.Lewis at
biogenidec.com>
>>>>>     on Mon, 14 Dec 2009 11:15:10 +0100 (CET) writes:
    JL> Full_Name: Jerry W. Lewis Version: 2.10.0 OS: XP
    JL> Professional Submission from: (NULL) (96.237.55.233)


    JL> For a degenerate Poisson distribution (lambda==0),
    JL> qpois(p,0,lower.tail) should return 0 for any valid p,
    JL> but qpois(1,0) and qpois(0,0,F) incorrectly return Inf.

It's very much a borderline case.

But you are right.  This will be fixed in the next versions of R,
but not yet in  R 2.10.1  released a few hours ago ... ;-)

Martin Maechler, ETH Zurich