Passing Arguments to Functions in stringi
Below we explain how stringi deals (in almost all the possible cases) with its functions' arguments.
Coercion of Arguments
When a character vector argument is expected, factors and other vectors
coercible to characters vectors
are silently converted with
otherwise an error is generated. When a logical, numeric or integer vector argument is expected,
factors are converted with
and other coercible vectors are converted with
otherwise an error is generated.
Almost all functions are vectorized with respect to all their arguments;
This may sometimes lead to strange results - we assume you know what
you are doing. However, due to this property you may,
e.g., search for one pattern in each given string,
or search for each pattern in one given string. 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
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.
Handling Missing Values (
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
Preserving Input Objects' Attributes
Generally, all our functions drop input objects' attributes
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, ...).