字符向量的R排序规则是什么？

Question

R 按我描述为字母而不是 ASCII 的序列对字符向量进行排序。

例如：

sort(c("dog", "Cat", "Dog", "cat"))
[1] "cat" "Cat" "dog" "Dog"

三个问题：

1. 描述这种排序顺序的技术正确术语是什么？
2. 我在 CRAN 的手册中找不到对此的任何参考。在哪里可以找到 R 中排序规则的说明？
3. 这与其他语言（如 C、Java、Perl 或 PHP）中的此类行为有什么不同？

Answer 1

Details: 代表sort() 状态：

 The sort order for character vectors will depend on the collating
 sequence of the locale in use: see ‘Comparison’.  The sort order
 for factors is the order of their levels (which is particularly
 appropriate for ordered factors).

然后help(Comparison) 显示：

 Comparison of strings in character vectors is lexicographicwithin
 the strings using the collating sequence of the locale in use:see
 ‘locales’.  The collating sequence of locales such as ‘en_US’ is
 normally different from ‘C’ (which should use ASCII) and can be
 surprising.  Beware of making _any_ assumptions about the 
 collation order: e.g. in Estonian ‘Z’ comes between ‘S’ and ‘T’,
 and collation is not necessarily character-by-character - in
 Danish ‘aa’ sorts as a single letter, after ‘z’.  In Welsh ‘ng’
 may or may not be a single sorting unit: if it is it follows ‘g’.
 Some platforms may not respect the locale and always sort in
 numerical order of the bytes in an 8-bit locale, or in Unicode
 point order for a UTF-8 locale (and may not sort in the same order
 for the same language in different character sets).  Collation of
 non-letters (spaces, punctuation signs, hyphens, fractions and so
 on) is even more problematic.

所以这取决于您的区域设置。

Answer 2

排序取决于语言环境。 我的解决方案如下...

我创建~/.Renviron 文件

cat ~/.Renviron 
#LC_ALL=C

那么在 R 中排序是在 C 语言环境中

x=c("A", "B", "d", "F", "g", "H")
sort(x)
#[1] "A" "B" "F" "H" "d" "g"