[R] qt with df<1 (repost)
Prof Brian Ripley
ripley at stats.ox.ac.uk
Sun Oct 12 15:34:49 CEST 2008
Please do RTFM, for the help says
df: degrees of freedom (> 0, maybe non-integer). 'df = Inf' is
allowed. For 'qt' only values of at least one are currently
On Sun, 12 Oct 2008, Enrico Rossi wrote:
> Sorry about the html-formatted message. Here it is again in plain text.
> The function qt returns NaN for degrees of freedom <1. For example:
>  NaN
> Warning message:
> In qt(p, df, lower.tail, log.p) : NaNs produced
> But qt(0.5,0.5) should be 0, since the distribution is symmetric.
>  0.5
> It actually fails with any value, as long as df<1.
> Is this a bug, or is there some fundamental reason why this cannot be
> Thank you,
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
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