mecab_wakati.R

# MeCabの{Rcpp}ラッパー定義
Sys.setenv("PKG_LIBS" = "-lmecab")
callRcppMecab <- Rcpp::cppFunction(
  code = '
  Rcpp::DataFrame executeMecab(std::string str, std::string tagger_opt) {
  using namespace Rcpp;
  using namespace MeCab;
  std::vector<std::string> surface, feature;
  MeCab::Tagger *tagger = MeCab::createTagger(tagger_opt.c_str());
  const MeCab::Node *node(tagger->parseToNode(str.c_str()));
  for (; node; node = node->next) {
  if (node->stat != MECAB_BOS_NODE & node->stat != MECAB_EOS_NODE) {
  surface.push_back(std::string(node->surface, node->length));
  feature.push_back(std::string(node->feature));
  }
  }
  delete tagger;
  return Rcpp::wrap(
  Rcpp::DataFrame::create(
  Rcpp::Named("surface") = surface,
  Rcpp::Named("feature") = feature
  )
  );
  }',
  includes = c("#include <mecab.h>")
)


# 形態素解析結果のうち、指定した品詞の表層のみを抽出
# @param text 形態素解析にかける入力文
# @param extract_pattern 抽出するパターン（正規表現）
mecab_wakati <- function (string, tagger_param = list(l = 2, d = NULL), extract_pattern) {
  if (length(x = tagger_param) > 0) {
    tagger_opt_str <- lapply(
      X = names(x = tagger_param),
      FUN = function (tg) {
        if (!is.null(x = tagger_param[[tg]]) & is.element(el = tg, set = c("l", "d"))) {
          return(
            stringr::str_c(stringr::str_c("-", tg), tagger_param[tg], sep = " ")
          )
        }
      }
    ) %>%
      unlist %>%
      stringr::str_c(collapse = " ")
  } else {
    tagger_opt_str <- ""
  }
  
  ex_surface <- callRcppMecab(str = as.character(x = string), tagger_opt = tagger_opt_str) %>%
    tidyr::separate(
      col = feature,
      into = c("pos", "pos1", "pos2", "pos3", "ctype", "cform", "baseform", "orth", "pron"),
      sep = ",", fill = "right"
    ) %>%
    dplyr::filter(stringr::str_detect(string = .$pos, pattern = extract_pattern)) %>%
    dplyr::mutate_if(.tbl = ., .predicate = is.factor, .funs = as.character) %>%
    dplyr::select(surface)
  
  if (nrow(x = ex_surface) < 1) {
    return("")
  } else {
    return(
      dplyr::summarize(ex_surface, sentence = stringr::str_c(surface, collapse = " ")) %>%
        .$sentence
    )
  }
}



extractContent(string = "私は大学へ行く",
               tagger_param = list(d = "/usr/local/lib/mecab/dic/mecab-ipadic-neologd"),
               extract_pattern = "名詞|形容詞")