[Rd] qf with infinite df

[Prof Brian Ripley]

On Thu, 5 Jun 2008, Simone Giannerini wrote:

> Dear all,
>
> I found the following behaviour
>
>> rf(5,Inf,Inf)
> [1] 1 1 1 1 1
>
> but
>
>> qf(0.1,Inf,Inf)
> [1] NaN
> Warning messages:
> 1: In qf(0.1, Inf, Inf) : value out of range in 'lgamma'
> 2: In qf(p, df1, df2, lower.tail, log.p) : NaNs produced

Could do better here.

> incidentally,
>
>
>> pf(1.00000000000001,Inf,Inf)
> [1] 1
>> pf(1.0000000000000001,Inf,Inf)
> [1] 0.5
>
> Is this the expected behaviour?

I think so. 1.0000000000000001 is the same as 1 in computer arithmetic, 
and pf(1, m, n) = 0.5 for all large m, n.

>
> Thanks
>
> Simone
>
>> R.version
>               _
> platform       i386-pc-mingw32
> arch           i386
> os             mingw32
> system         i386, mingw32
> status         Patched
> major          2
> minor          7.0
> year           2008
> month          04
> day            22
> svn rev        45451
> language       R
> version.string R version 2.7.0 Patched (2008-04-22 r45451)
>
> platform       x86_64-unknown-linux-gnu
> arch           x86_64
> os             linux-gnu
> system         x86_64, linux-gnu
> status         Patched
> major          2
> minor          6.1
> year           2008
> month          01
> day            17
> svn rev        44036
> language       R
> version.string R version 2.6.1 Patched (2008-01-17 r44036)
>
> ______________________________________________________
>
> Simone Giannerini
> Dipartimento di Scienze Statistiche "Paolo Fortunati"
> Universita' di Bologna
> Via delle belle arti 41 - 40126 Bologna, ITALY
> Tel: +39 051 2098262 Fax: +39 051 232153
> http://www2.stat.unibo.it/giannerini/
> ______________________________________________________
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
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>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595