The EMU Speech Database System. Natural Language Processing. Natural language processing has come a long way since its foundations were laid in the 1940s and 50s (for an introduction see, e.g., Jurafsky and Martin (2008): Speech and Language Processing, Pearson Prentice Hall). This CRAN task view collects relevant R packages that support computational linguists in conducting analysis of speech and language on a variety of levels - setting focus on words, syntax, semantics, and pragmatics.
In recent years, we have elaborated a framework to be used in packages dealing with the processing of written material: the package tm. Extension packages in this area are highly recommended to interface with tm's basic routines and useRs are cordially invited to join in the discussion on further developments of this framework package. To get into natural language processing, the cRunch service and tutorials may be helpful.
Frameworks: tm provides a comprehensive text mining framework for R. Semantics: Pragmatics: Tm - Text Mining Package. Regular Expressions with grep, regexp and sub in the R Language. The R Project for Statistical Computing provides seven regular expression functions in its base package. The R documentation claims that the default flavor implements POSIX extended regular expressions. That is not correct. In R 2.10.0 and later, the default regex engine is a modified version of Ville Laurikari's TRE engine. It mimics POSIX but deviates from the standard in many subtle and not-so-subtle ways. What this website says about POSIX ERE does not (necessarily) apply to R. Older versions of R used the GNU library to implement both POSIX BRE and ERE.
ERE was the default. The best way to use regular expressions with R is to pass the perl=TRUE parameter. All the functions use case sensitive matching by default. Finding Regex Matches in String Vectors The grep function takes your regex as the first argument, and the input vector as the second argument. > grepl("a+", c("abc", "def", "cba a", "aa"), perl=TRUE) [1] TRUE FALSE TRUE TRUE Replacing Regex Matches in String Vectors.
R - Regex Guru.