Below we explain how stringi deals (in most of the cases) with its functions' arguments.
When a character vector argument is expected, factors and other vectors
coercible to characters vectors
are silently converted with as.character,
otherwise an error is generated.
Coercion from a list of non-atomic vectors each of length 1
issues a warning.
When a logical, numeric, or integer vector argument is expected,
factors are converted with as.*(as.character(...)),
and other coercible vectors are converted with as.*,
otherwise an error is generated.
Almost all functions are vectorized with respect to all their arguments and the recycling rule is applied whenever necessary. Due to this property you may, for instance, search for one pattern in each given string, search for each pattern in one given string, and search for the i-th pattern within the i-th string. This behavior sometimes leads to peculiar results - we assume you know what you are doing.
We of course took great care of performance issues: e.g., in regular expression searching, regex matchers are reused from iteration to iteration, as long it is possible.
Functions with some non-vectorized arguments are rare: e.g., regular expression matcher's settings are established once per each call.
Some functions
assume that a vector with one element is given
as an argument (like collapse in stri_join).
In such cases, if an empty vector is given you will get an error
and for vectors with more than 1 elements - a warning will be
generated (only the first element will be used).
You may find details on vectorization behavior in the man pages on each particular function of your interest.
stringi handles missing values consistently.
For any vectorized operation, if at least one vector element is missing,
then the corresponding resulting value is also set to NA.
Generally, all our functions drop input objects' attributes
(e.g., names, dim, etc.).
This is generally because of advanced vectorization and for efficiency reasons.
Thus, if arguments' preserving is needed,
please remember to copy important attributes manually
or use, e.g., the subsetting operation like x[] <- stri_...(x, ...).
Other stringi_general_topics:
about_encoding,
about_locale,
about_search_boundaries,
about_search_charclass,
about_search_coll,
about_search_fixed,
about_search_regex,
about_search,
about_stringi