[Rd] Reading Inf and NaN values under windows (PR#1072)

[Prof Brian Ripley]

On Fri, 24 Aug 2001 plummer@iarc.fr wrote:

> Under windows, R supports IEEE floating point arithmetic, but doesn't
> allow conversion of Inf and NaN from character to numeric.
>
> R> is.nan(NaN)
> [1] TRUE
> R> as.numeric(as.character(NaN))
> [1] NA
> Warning message:
> NAs introduced by coercion
> R> is.infinite(Inf)
> [1] TRUE
> R> as.numeric(as.character(Inf))
> [1] NA
> Warning message:
> NAs introduced by coercion
>
> whereas under Linux
>
> R> as.numeric(as.character(NaN))
> [1] NaN
> R> as.numeric(as.character(Inf))
> [1] Inf
>
> S-PLUS 3.3 for Windows gives
>
> S-PLUS> as.numeric(as.character(Inf))
> [1] Inf
> S-PLUS> as.numeric(as.character(NaN))
> [1] NA
> Warning messages:
>   1 missing value  generated coercing from character to numeric in:
>         as.numeric(as.character(NaN))
>
> I first came across this problem when trying to read in a dataset with
> Inf values using read.table().  Under Windows, the variable with the
> infinite value is converted to a factor. The scan() function also refuses
> to read in Inf and NaN as numeric values under Windows.

It's the same cause: strtod is used.  That's not required to support
IEC 60559 (to be correct) specials, but glibc happens to.

We have R_strtod: we should make proper use of it.  I'll do that for
1.3.1.

Brian

>
> Martyn
>
> --please do not edit the information below--
>
> Version:
>  platform = i386-pc-mingw32
>  arch = x86
>  os = Win32
>  system = x86, Win32
>  status =
>  major = 1
>  minor = 3.0
>  year = 2001
>  month = 06
>  day = 22
>  language = R
>
> Windows NT 4.0 (build 1381) Service Pack 6
>
> Search Path:
>  .GlobalEnv, package:ctest, Autoloads, package:base
>
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-- 
Brian D. Ripley,                  ripley@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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