RcppMeCab

This package, RcppMeCab, is a Rcpp wrapper for the part-of-speech morphological analyzer MeCab. It supports native utf-8 encoding in C++ code and CJK (Chinese, Japanese, and Korean) MeCab library. This package fully utilizes the power Rcpp brings R computation to analyze texts faster.

__Please see this for easy installation and usage examples in Korean.__

MeCab backends

RcppMeCab builds MeCab from source at install time. The MeCab variant is selected by the MECAB_LANG environment variable:

On Linux and macOS, if MeCab is already installed system-wide (detected via mecab-config), RcppMeCab uses the system installation regardless of MECAB_LANG.

Installation

Linux, macOS, and Windows

RcppMeCab automatically downloads and builds MeCab from source if it is not already installed on your system. No manual MeCab installation is required.

install.packages("RcppMeCab") # install from CRAN

# or install the development version
# install.packages("devtools")
devtools::install_github("junhewk/RcppMeCab")

If you already have MeCab installed (e.g. via brew install mecab on macOS, or apt install libmecab-dev on Linux), RcppMeCab will use your system installation.

Language selection

Set MECAB_LANG before installation to choose the MeCab variant:

# Korean (default)
install.packages("RcppMeCab", type = "source")

# Japanese
Sys.setenv(MECAB_LANG = "ja")
install.packages("RcppMeCab", type = "source")

Dictionary

A MeCab dictionary is automatically downloaded and installed during package installation:

• Korean (MECAB_LANG=ko, default): mecab-ko-dic (pre-compiled, from mecab-ko-msvc releases)
• Japanese (MECAB_LANG=ja): IPAdic (compiled from source during installation)

The bundled dictionary is stored in the package's dic/ directory and used automatically — no manual dictionary setup is required.

Downloading additional dictionaries

You can download and install dictionaries for other languages after installation using download_dic(). No system-level MeCab installation is required — dictionary compilation is handled entirely within R.

download_dic("ja") # download and compile Japanese IPAdic
download_dic("ko") # download Korean mecab-ko-dic
download_dic("zh") # download and compile Chinese mecab-jieba

Dictionaries are stored in the user data directory (tools::R_user_dir("RcppMeCab", "data")) and persist across R sessions.

Use list_dic() to see all installed dictionaries:

list_dic()
#>      lang         name                              path active
#> 1 bundled      bundled /path/to/RcppMeCab/dic              TRUE
#> 2      ja       ipadic ~/.local/share/R/RcppMeCab/ja      FALSE
#> 3      ko mecab-ko-dic ~/.local/share/R/RcppMeCab/ko      FALSE
#> 4      zh  mecab-jieba ~/.local/share/R/RcppMeCab/zh      FALSE

Usage

This package has pos and posParallel functions.

pos(sentence)                        # returns a list
pos(sentence, join = FALSE)          # morphemes only (tags as vector names)
pos(sentence, format = "data.frame") # returns a data frame
pos(sentence, user_dic = "path")     # with a compiled user dictionary
posParallel(sentence)                # parallelized, faster for large inputs

Switching languages

Use the lang parameter to select a dictionary by language:

pos("東京は日本の首都です。", lang = "ja")
pos("안녕하세요", lang = "ko")
pos("我是中国人。", lang = "zh")

Or set a default with set_dic():

set_dic("ja")
pos("東京は日本の首都です。") # uses Japanese dictionary
set_dic("ko")
pos("안녕하세요")              # uses Korean dictionary
set_dic("bundled")             # switch back to the build-time dictionary

You can also specify a custom dictionary path directly:

pos("text", sys_dic = "/path/to/custom-dic")
options(mecabSysDic = "/path/to/custom-dic")

Parameters

• sentence: text to analyze
• join: if TRUE (default), output is morpheme/tag; if FALSE, output is morpheme with tag as attribute
• format: "list" (default) or "data.frame"
• lang: language code ("ja", "ko", or "zh") to select a dictionary installed via download_dic(). Overrides sys_dic when specified.
• sys_dic: directory containing dicrc, sys.dic, etc. Set a default with options(mecabSysDic = "/path/to/dic")
• user_dic: path to a user dictionary compiled by dict_index()

Note: provide full paths for sys_dic and user_dic (no tilde ~/ expansion).

Compiling a user dictionary

RcppMeCab provides the dict_index() function to compile user dictionaries directly from R, without needing the mecab-dict-index command-line tool.

Prepare your entries as a CSV file (Japanese format, Korean format), then compile:

dict_index(
  dic_csv = "entries.csv",
  out_dic = "userdic.dic",
  dic_dir = "/path/to/mecab-dic"
)

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

Authors

Junhewk Kim ([email protected]), Taku Kudo

Contributors

Akiru Kato, Patrick Schratz