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# stri_sort_key: Sort Keys

## Description

This function computes a locale-dependent sort key, which is an alternative character representation of the string that, when ordered in the C locale (which orders using the underlying bytes directly), will give an equivalent ordering to the original string. It is useful for enhancing algorithms that sort only in the C locale (e.g., the `strcmp` function in libc) with the ability to be locale-aware.

## Usage

    stri_sort_key(str, ..., opts_collator = NULL)

## Arguments

`str` | a character vector
`...` | additional settings for `opts_collator`
`opts_collator` | a named list with ICU Collator’s options, see `stri_opts_collator`, `NULL` for default collation options

## Details

For more information on ICU’s Collator and how to tune it up in stringi, refer to `stri_opts_collator`.

See also `stri_rank` for ranking strings with a single character vector, i.e., generating relative sort keys.

## Value

The result is a character vector with the same length as `str` that contains the sort keys. The output is marked as `bytes`-encoded.

## Author(s)

Marek Gagolewski and other contributors

## References

Collation - ICU User Guide, https://unicode-org.github.io/icu/userguide/collation/

## See Also

The official online manual of stringi at https://stringi.gagolewski.com/

Gagolewski M., stringi: Fast and portable character string processing in R, Journal of Statistical Software 103(2), 2022, 1-59, doi:10.18637/jss.v103.i02

Other locale_sensitive: `%s<%()`, `about_locale`, `about_search_boundaries`, `about_search_coll`, `stri_compare()`, `stri_count_boundaries()`, `stri_duplicated()`, `stri_enc_detect2()`, `stri_extract_all_boundaries()`, `stri_locate_all_boundaries()`, `stri_opts_collator()`, `stri_order()`, `stri_rank()`, `stri_sort()`, `stri_split_boundaries()`, `stri_trans_tolower()`, `stri_unique()`, `stri_wrap()`

## Examples

    stri_sort_key(c('hladny', 'chladny'), locale='pl_PL')
    ## [1] "8@*0DZ\001\n\001\n"  ".8@*0DZ\001\v\001\v"
    stri_sort_key(c('hladny', 'chladny'), locale='sk_SK')
    ## [1] "8@*0DZ\001\n\001\n"     "9\002@*0DZ\001\n\001\n"