[R] NaN/NA and sprintf double format
ripley at stats.ox.ac.uk
Tue May 14 20:56:05 CEST 2002
On Tue, 14 May 2002, Dirk Eddelbuettel wrote:
> With a (late prerelease of) 1.5.0 on Windows, using sprintf on NaN
> yields garbage when the number of decimal is specified while it
> works fine for NA:
> > sprintf("%.2f", NA)
>  "0.00"
I get that on Linux too, but why is it fine? See below.
> > sprintf("%.2f", NaN)
>  "-1.#J"
> Not specifying the decimal precision lets both print garbage:
> > sprintf("%f", NaN)
>  "-1.#IND00"
> > sprintf("%f", NA)
>  "-1.#QNAN0"
> Is this a bug or a feature?
Remember that NA is logical, so this is not correct usage. Not that the
correct usage works very much better ....
The C code says
/* Simple wrapper for C sprintf function: does very little checking to
see that the format conversion character and the argument are
compatible. This is the user's responsibility!
and I think that should be on the help page. If it were, this is a
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 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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