Table 的 n-gram 并识别文本出现的行

Question

我想构建一个 table，其中 n-gram 显示为一列和构建它们的数据帧的行号。

例如，下面的代码用于构造 n-gram（在本例中为四元组）：

# Libraries
library(quanteda)
library(data.table)
library(tidyverse)
library(stringr)

# Dataframe
Data <- data.frame(Column1 = c(1.222, 3.445, 5.621, 8.501, 9.302), 
                  Column2 = c(654231, 12347, -2365, 90000, 12897), 
                  Column3 = c('A1', 'B2', 'E3', 'C1', 'F5'), 
                  Column4 = c('I bought it', 'The flower has a beautiful fragrance', 'It was bought by me', 'I have bought it', 'The flower smells good'), 
                  Column5 = c('Good', 'Bad', 'Ok', 'Moderate', 'Perfect'))

# Text column of interest
TextColumn <- Data$Column4

# Corpus
Content <-  corpus(TextColumn)

# Tokenization
Tokens <- tokens(Content, what = "word",
                               remove_punct = TRUE,
                               remove_symbols = TRUE,
                               remove_numbers = FALSE,
                               remove_url = TRUE,
                               remove_separators = TRUE,
                               split_hyphens = FALSE,
                               include_docvars = TRUE,
                               padding = FALSE)

Tokens <- tokens_tolower(Tokens)

# n-grams

quadgrams <- dfm(tokens_ngrams(Tokens, n = 4))
quadgrams_freq <- textstat_frequency(quadgrams)                  # quadgram frequency
quadgrs <- subset(quadgrams_freq,select=c(feature,frequency))
names(quadgrs) <- c("ngram","freq")
quadgrs <- as.data.table(quadgrs)

结果是

有没有办法从 Column4 中提取单词的行号。例如，包含 2（行号）的列必须在上面 table 中对应于“the_flower_has_a”，并且再次将 2（行号）作为“flower_has_a_beautiful”的条目等.

Answer 1

您可以在textstat_frequency()中指定一个与组名相对应的组，这将提供对您原始“行号”的引用。

library("quanteda")
## Package version: 2.1.2

library("data.table")

# Dataframe
Data <- data.frame(
  Column1 = c(1.222, 3.445, 5.621, 8.501, 9.302),
  Column2 = c(654231, 12347, -2365, 90000, 12897),
  Column3 = c("A1", "B2", "E3", "C1", "F5"),
  Column4 = c("I bought it", "The flower has a beautiful fragrance", "It was bought by me", "I have bought it", "The flower smells good"),
  Column5 = c("Good", "Bad", "Ok", "Moderate", "Perfect")
)

# Corpus
Content <- corpus(Data, text_field = "Column4")
docnames(Content) <- seq_len(nrow(Data))

# Tokenization and ngrams
Tokens <- tokens(Content,
  what = "word",
  remove_punct = TRUE,
  remove_symbols = TRUE,
  remove_url = TRUE
) %>%
  tokens_tolower() %>%
  tokens_ngrams(n = 4)

现在是小组部分：

# form the result
quadgrs <- textstat_frequency(dfm(Tokens), groups = docnames(Tokens)) %>%
  as.data.table()
setnames(quadgrs, "group", "rownumber")

quadgrs[, c("feature", "frequency", "rownumber")]
##                      feature frequency rownumber
## 1:          the_flower_has_a         1         2
## 2:    flower_has_a_beautiful         1         2
## 3: has_a_beautiful_fragrance         1         2
## 4:          it_was_bought_by         1         3
## 5:          was_bought_by_me         1         3
## 6:          i_have_bought_it         1         4
## 7:    the_flower_smells_good         1         5

注意：

我稍微简化了您的代码，因为其中一些代码是不必要的或可以简化的。
频率计数现在在行（文档）内，因此如果您在多行中有相同的 ngram，它将在输出 table 中出现不止一次，频率在行内。如果您想重复出现在多行中的 ngram 的总体频率，则可以轻松修改此代码以反映这一点。（如果你想要那个，请告诉我。）

Table 的 n-gram 并识别文本出现的行

Table of n-grams and identifying the row in which the text appeared

r

nlp

text-mining

n-gram

quanteda