[Rd] Windows, format.POSIXct and character encodings

[Simon Urbanek]

On May 1, 2013, at 10:06 AM, Hadley Wickham wrote:

> Hi all,
> 
> In what encoding does format.POSIXct return its output? It doesn't
> seem to be utf-8:
> 
> Sys.setlocale("LC_ALL", "Japanese_Japan.932")
> 
> times <- c("1970-01-01 01:00:00 UTC", "1970-02-02 22:00:00 UTC")
> ampm <- format(as.POSIXct(times), format = "%p")
> x <- gsub(">", "*", paste(ampm, collapse = "+>"))
> 
> y <- "午前+*午後"
> identical(x, y)
> # [1] TRUE
> 
> # But, confusingly, ...
> 
> charToRaw(x)
> # [1] e5 8d 88 e5 89 8d 2b 2a e5 8d 88 e5 be 8c
> 
> charToRaw(y)
> # [1] 8c df 91 4f 2b 2a 8c df 8c e3
> 

That's not confusing at all:

> Encoding(x)
[1] "UTF-8"
> Encoding(y)
[1] "unknown"

The first string is in UTF-8 the second is in the local locale (here 932).


> # So there's at least a small bug with identical
> 

Nope: ?identical
"Character strings are regarded as identical if they are in different marked encodings but would agree when translated to UTF-8."


> # And this causes a problem when you attempt to do
> # stuff with the string
> 
> gsub("+", "*", x, fixed = T)
> # Error in gsub("+", "*", x, fixed = T) :
> #  invalid multibyte string at '<8c>'
> gsub("+", "*", y, fixed = T)
> # [1] "午前**午後"
> 

This is where the problem lies - and it has nothing to do with format:

> z=enc2utf8("午前+*午後")
> gsub("+", "*", z, fixed = T)
Error in gsub("+", "*", z, fixed = T) : 
  invalid multibyte string at '<8c>'

The cause is that  fgrep_one() gives higher precedence to mbcslocale than use_UTF8 so the grep is actually done in the MBCS locale and not UTF-8. Consequently, you'll see this only in multi-byte locales other than UTF-8, so on let's say OS X you can reproduce it with

> x="午前+*午後"
> gsub("+", "*", x, fixed = T)
Error in gsub("+", "*", x, fixed = T) : 
  invalid multibyte string at '<8c>'

Inverting the precedence would fix this issue, but I'm not sure if it would have unwanted side-effects on MBCS locales ...

Cheers,
Simon


> 
> My session info is
> 
> R version 3.0.0 (2013-04-03)
> Platform: x86_64-w64-mingw32/x64 (64-bit)
> 
> locale:
> [1] LC_COLLATE=Japanese_Japan.932  LC_CTYPE=Japanese_Japan.932
> [3] LC_MONETARY=Japanese_Japan.932 LC_NUMERIC=C
> [5] LC_TIME=Japanese_Japan.932
> 
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
> 
> loaded via a namespace (and not attached):
> [1] tools_3.0.0
> 
> Any ideas? Thanks!
> 
> Hadley
> 
> --
> Chief Scientist, RStudio
> http://had.co.nz/
> 
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