Re: [Rd] qchisq (PR#7212)

From: Peter Dalgaard <p.dalgaard_at_biostat.ku.dk>
Date: Tue 07 Sep 2004 - 02:46:06 EST

david.clayton@cimr.cam.ac.uk writes:

> Full_Name: David Clayton
> Version: 1.8.1
....
> qchisq behaves very strangely when ncp is passed as zero (forcing internal
> qnchisq to be called) when first argument is small.
>
> Eg
>
>
> > qchisq(1-1e-6, 1, ncp=0, lower.tail=TRUE)
> qchisq(1-1e-6, 1, ncp=0, lower.tail=TRUE)
> [1] 1024
>
> while, if ncp is unspecified,
>
> > qchisq(1-1e-6, 1)
> qchisq(1-1e-6, 1)
> [1] 23.92813

As Brian once put it, we can't fix old versions retroactively. 1.9.1 has (on "Linux" as well, although that is a bit unspecific for numeric issues).

> qchisq(1-1e-6, 1, ncp=0, lower.tail=TRUE)
[1] 23.92813
> qchisq(1-1e-6, 1)

[1] 23.92813

Possibly, this is a side effect of

    o qchisq(1-e, .., ncp=.) did not terminate for small e.

        (PR#6421 (PR#875))

from BUG FIXES for 1.9.0.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907

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Received on Tue Sep 07 02:49:42 2004

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