从字符串中获取最后 10 个单词，应用于字符串向量

Posted 2023-02-14

【中文标题】从字符串中获取最后 10 个单词，应用于字符串向量

【英文标题】：getting the last 10 words from a string, applied on a vector of strings

【发布时间】：2022-01-21 06:28:39

【问题描述】：

我在数据框 (df1$text) 中有一个文本向量，我正在尝试使用文本的最后 10 个单词 (df1$last.ten) 创建一个新向量。我尝试了以下方法但没有成功：

df1$last.ten = mapply(function(x,y) paste(word(x,y), collapse=" "), df1$text, -1:-10)

但是我得到的只是一个词而不是一串十个词：

> df1$last.ten[1]
[1] "end."

当我给它一个字符串时它工作得很好，所以我似乎错误地使用了mapply。

我已尝试为此使用gsub，但无法弄清楚语法。将不胜感激word() 或gsub() 解决方案。

【参考方案1】：

如果这是你的数据框（玩具数据）

df1
                                                            text
1 one two three four five six seven eight nine ten eleven twelve
2 one two three four five six seven eight nine ten eleven twelve
3 one two three four five six seven eight nine ten eleven twelve

然后像这样提取最后10个单词

rnge <- 10:1

df1$last.ten <- apply( t(apply( as.data.frame(df1$text), 1, function(x)
  rev( unlist( strsplit(x, " ") ) ) )[rnge,]), 1, paste, collapse=" " )

df1
                                                            text
1 one two three four five six seven eight nine ten eleven twelve
2 one two three four five six seven eight nine ten eleven twelve
3 one two three four five six seven eight nine ten eleven twelve
                                                last.ten
1 three four five six seven eight nine ten eleven twelve
2 three four five six seven eight nine ten eleven twelve
3 three four five six seven eight nine ten eleven twelve

如果您调整范围rnge，这将从任何地方提取数据

rnge <- 5:3

df1$mid <- apply( t(apply( as.data.frame(df1$text), 1, function(x)
  rev( unlist( strsplit(x, " ") ) ) )[rnge,]), 1, paste, collapse=" " )

df1
                                                            text
1 one two three four five six seven eight nine ten eleven twelve
2 one two three four five six seven eight nine ten eleven twelve
3 one two three four five six seven eight nine ten eleven twelve
                                                last.ten            mid
1 three four five six seven eight nine ten eleven twelve eight nine ten
2 three four five six seven eight nine ten eleven twelve eight nine ten
3 three four five six seven eight nine ten eleven twelve eight nine ten

【参考方案2】：

我制作了一些示例数据。也许你不需要使用 apply 函数。

df1 <- data.frame(text = c("one two three four five six seven eight nine ten eleven","one two three four five six seven eight nine ten eleven twelve"))


df1$last.ten <- word(df1[[1]], str_count(df1[[1]], '\\w+') - 9, str_count(df1[[1]], '\\w+'))

【参考方案3】：

这是一个基本的 R 选项 -

#example data
df1 <- data.frame(text = c('This is a long text which consists of words more than 10', 
                           'This is another one which is similar to first one but even longer'))

#split string on space for every word and paste the last 10 words in one string
df1$last.ten <- sapply(strsplit(df1$text, '\\s+'), function(x) 
                       paste0(tail(x, 10), collapse = ' '))
df1