¿Cuáles son las reglas de clasificación R de los vectores de caracteres?

Question

R ordena los vectores de caracteres en una secuencia que describo como alfabética, no como ASCII.

Por ejemplo:

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

tres preguntas:

1. ¿Cuál es la terminología técnicamente correcta para describir este orden?
2. No encuentro ninguna referencia al respecto en los manuales de CRAN. ¿Dónde puedo encontrar una descripción de las reglas de clasificación en R?
3. ¿Es esto diferente de este tipo de comportamiento en otros lenguajes como C, Java, Perl o PHP?

Answer 1

Details: para sort() estados:

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). 

y help(Comparison) muestra a continuación:

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. 

por lo que depende de su configuración local.