Package {RcppMeCab}

RcppMeCab: Rcpp Wrapper for MeCab Library

Description

R package based on Rcpp for MeCab: Yet Another Part-of-Speech and Morphological Analyzer (http://taku910.github.io/mecab/). It provides install-time engine profiles and dictionaries for Japanese, Korean, and Mandarin Chinese text. Runtime dictionary selection does not change the installed engine. This package utilizes parallel programming for providing highly efficient text preprocessing posParallel() function. For installation, please refer to README.md file.

Details

This package utilizes MeCab C API and Rcpp codes.

Author(s)

Junhewk Kim Taku Kudo

References

• MeCab

• Rcpp: Seamless R and C++ Integration

• Eunjeon project

See Also

Useful links:

• Report bugs at https://github.com/junhewk/RcppMeCab/issues

Compile a MeCab user dictionary

Description

dict_index compiles a user dictionary CSV file into a binary dictionary that can be used with pos and posParallel.

Usage

dict_index(
  dic_csv,
  out_dic,
  dic_dir,
  dic_charset = "utf-8",
  out_charset = "utf-8"
)

Arguments

Details

This function wraps MeCab's mecab-dict-index internally, so you do not need the command-line tool installed separately.

Value

Invisible TRUE on success.

Examples

## Not run: 
dict_index(
  dic_csv = "user_words.csv",
  out_dic = "user.dic",
  dic_dir = "/usr/local/lib/mecab/dic/ipadic"
)

# Then use the compiled dictionary:
pos("some text", user_dic = "user.dic")

## End(Not run)

Inspect loaded MeCab dictionaries

Description

Returns metadata reported by MeCab for the active system and user dictionaries. This is useful for diagnosing which dictionary a package or R session is actually using.

Usage

dictionary_info(sys_dic = "", user_dic = "")

Arguments

Value

A data frame with one row per loaded dictionary and columns filename, charset, type, size, left_size, right_size, and version.

Examples

## Not run: 
dictionary_info()

## End(Not run)

Download and install a MeCab dictionary

Description

Downloads and installs a MeCab system dictionary for the specified language. Japanese and Chinese dictionaries are compiled from source using the built-in mecab-dict-index; Korean dictionaries are downloaded pre-compiled. No system-level MeCab installation is required.

Installing a dictionary does not change the MeCab engine linked into RcppMeCab. Japanese and Chinese dictionaries use standard MeCab. Supported Korean behavior requires the mecab-ko engine selected at package installation.

Usage

download_dic(lang)

Arguments

Details

Dictionaries are stored in the user data directory (tools::R_user_dir("RcppMeCab", "data")).

Value

Invisible path to the installed dictionary directory.

Examples

## Not run: 
download_dic("ja")
download_dic("ko")
download_dic("zh")
pos("some text", lang = "ja")

## End(Not run)

List installed MeCab dictionaries

Description

Shows all available MeCab dictionaries, including the bundled dictionary and any downloaded via download_dic.

Usage

list_dic()

Value

A data frame with columns lang, name, path, and active.

Examples

## Not run: 
list_dic()

## End(Not run)

part-of-speech tagger

Description

pos returns part-of-speech (POS) tagged morpheme of the sentence.

Usage

pos(
  sentence,
  join = TRUE,
  format = c("list", "data.frame"),
  lang = NULL,
  sys_dic = "",
  user_dic = ""
)

Arguments

Details

This is a basic function for MeCab part-of-speech tagger. The function gets a character vector of any length and runs a loop inside C++ to provide faster processing.

You can add a user dictionary to user_dic. It should be compiled by mecab-dict-index. You can find an explanation about compiling a user dictionary in the https://github.com/junhewk/RcppMeCab.

You can also set a system dictionary especially if you are using multiple dictionaries (for example, using both IPA and Juman dictionary at the same time in Japanese) in sys_dic. Using options(mecabSysDic=), you can set your preferred system dictionary to the R terminal.

The lang argument selects a dictionary; it does not switch the MeCab engine chosen when RcppMeCab was installed. Japanese and Chinese dictionaries use standard MeCab. Supported Korean behavior, including mecab-ko whitespace handling, requires the mecab-ko engine. Dictionary feature layouts are language-specific, and the historical data-frame columns do not expose all mecab-jieba metadata.

If you want to get a morpheme only, use join = False to put tag names on the attribute. Basically, the function will return a list of character vectors with (morpheme)/(tag) elements.

Value

A string vector or a list of POS tagged morpheme will be returned in conjoined character vector form.

Examples

## Not run: 
sentence <- c(#some UTF-8 texts)
pos(sentence)
pos(sentence, join = FALSE)
pos(sentence, format = "data.frame")
pos(sentence, lang = "ja")
pos(sentence, lang = "zh")
pos(sentence, sys_dic = "/path/to/custom/dic")
pos(sentence, user_dic = "/path/to/user.dic")

## End(Not run)

parallel version of part-of-speech tagger

Description

posParallel returns part-of-speech (POS) tagged morpheme of the sentence.

Usage

posParallel(
  sentence,
  join = TRUE,
  format = c("list", "data.frame"),
  lang = NULL,
  sys_dic = "",
  user_dic = ""
)

Arguments

Details

This is a parallelized version of MeCab part-of-speech tagger. The function gets a character vector of any length and runs a loop inside C++ with Intel TBB to provide faster processing.

Parallelizing over a character vector is not supported by RcppParallel. Thus, this function makes duplicates of the input and the output. Therefore, if your data volume is large, use pos or divide the vector to several sub-vectors.

You can add a user dictionary to user_dic. It should be compiled by mecab-dict-index. You can find an explanation about compiling a user dictionary in the https://github.com/junhewk/RcppMeCab.

You can also set a system dictionary especially if you are using multiple dictionaries (for example, using both IPA and Juman dictionary at the same time in Japanese) in sys_dic. Using options(mecabSysDic=), you can set your preferred system dictionary to the R terminal.

The lang argument selects a dictionary; it does not switch the MeCab engine chosen when RcppMeCab was installed. Japanese and Chinese dictionaries use standard MeCab. Supported Korean behavior, including mecab-ko whitespace handling, requires the mecab-ko engine. Dictionary feature layouts are language-specific, and the historical data-frame columns do not expose all mecab-jieba metadata.

If you want to get a morpheme only, use join = False to put tag names on the attribute. Basically, the function will return a list of character vectors with (morpheme)/(tag) elements.

Value

A string vector or a list of POS tagged morpheme will be returned in conjoined character vector form.

Examples

## Not run: 
sentence <- c(#some UTF-8 texts)
posParallel(sentence)
posParallel(sentence, join = FALSE)
posParallel(sentence, format = "data.frame")
posParallel(sentence, lang = "ja")
posParallel(sentence, lang = "zh")
posParallel(sentence, sys_dic = "/path/to/custom/dic")
posParallel(sentence, user_dic = "/path/to/user.dic")

## End(Not run)

Set the active MeCab dictionary

Description

Sets the default system dictionary used by pos and posParallel. This is equivalent to calling options(mecabSysDic = path) but allows selection by dictionary code. It does not switch the MeCab engine linked into RcppMeCab. Japanese and Chinese dictionaries use standard MeCab; supported Korean behavior requires the mecab-ko engine selected at package installation.

Usage

set_dic(lang)

Arguments

Value

Invisible path to the activated dictionary directory.

Examples

## Not run: 
set_dic("ja")
pos("some Japanese text")

set_dic("zh")
pos("some Chinese text")

## End(Not run)