字符向量的R排序规则是什么? [英] What are the R sorting rules of character vectors?

问题描述

R按我描述为字母而不是ASCII的顺序对字符向量进行排序.

R sorts character vectors in a sequence which I describe as alphabetic, not ASCII.

例如:

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

三个问题:

1. 描述此排序顺序的技术上正确的术语是什么?
2. 我在CRAN的手册中找不到对此的任何引用.在哪里可以找到有关R中排序规则的描述?
3. 与其他语言(例如C，Java，Perl或PHP)中的这种行为有什么不同吗?

推荐答案

Details:用于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).

和help(Comparison)然后显示:

 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.

所以这取决于您的语言环境设置.

so it depends on your locale setting.

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