about_search_boundaries: Text Boundary Analysis in stringi
Text boundary analysis is the process of locating linguistic boundaries while formatting and handling text.
Examples of the boundary analysis process include:
Counting characters, words, sentences, or paragraphs, see
Capitalizing the first letter of each word or sentence, see also
Locating a particular unit of the text (for example, finding the third word in the document), see
Generally, text boundary analysis is a locale-dependent operation. For example, in Japanese and Chinese one does not separate words with spaces - a line break can occur even in the middle of a word. These languages have punctuation and diacritical marks that cannot start or end a line, so this must also be taken into account.
stringi uses ICU’s
BreakIterator to locate specific text boundaries. Note that the
BreakIterator’s behavior may be controlled in come cases, see
characterboundary iterator tries to match what a user would think of as a “character” – a basic unit of a writing system for a language – which may be more than just a single Unicode code point.
wordboundary iterator locates the boundaries of words, for purposes such as “Find whole words” operations.
line_breakiterator locates positions that would be appropriate to wrap lines when displaying the text.
The break iterator of type
sentencelocates sentence boundaries.
For technical details on different classes of text boundaries refer to the ICU User Guide, see below.
Boundary Analysis – ICU User Guide, https://unicode-org.github.io/icu/userguide/boundaryanalysis/
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