Setup Collation by ICU
Controls the way collation is done by ICU (an optional part of the R build).
- Named arguments, see Details.
Optionally, R can be built to collate character strings by ICU
(http://site.icu-project.org). For such systems,
icuSetCollate can be used to tune the way collation is done.
On other builds calling this function does nothing, with a warning.
Possible arguments are
- A character string such as
"da_DK"giving the country whose collation rules are to be used. If present, this should be the first argument.
"default", asking for upper- or lower-case characters to be sorted first. The default is usually lower-case first, but not in all languages (see the Danish example).
"non_ignorable"(primary strength) and
"off"(default). This affects the collation of composite characters.
"on"(sort Hiragana first at quaternary level) and
Only the first three are likely to be of interest except to those with a detailed understanding of collation and specialized requirements.
Some examples are
case_level = "on", strength = "primary" to ignore
accent differences and
alternate_handling = "shifted" to ignore
space and punctuation characters.
Note that these settings have no effect if collation is set to the
C locale, unless
locale is specified.
ICU is used by default wherever it is available: this include Mac OS >= 10.4 and many Linux installations.
The ICU user guide chapter on collation (http://userguide.icu-project.org/collation).