正则表达式和字符串包 [英] RegEx and stringr package

问题描述

我是 R 新手，我的编程作业有问题.

I am an R newbie and have troubles with my programming homework.

输入是一首诗:

poem <- c(
  "Am Tag, an dem das L verschwand,", 
  "da war die Luft voll Klagen.",
  "Den Dichtern, ach, verschlug es glatt",
  "ihr Singen und ihr Sagen.",
  "Nun gut. Sie haben sich gefasst.",
  "Man sieht sie wieder schreiben.",
  "Jedoch:",
  "Solang das L nicht wiederkehrt,",
  "muß alles Flickwerk beiben.")

现在我需要提取所有大写字母并将它们组合成一个单词.我正在使用以下代码执行此操作:

Now I need to extract all the capital letters and combine them into one word. I am doing this with the following code:

poem_cap <- str_extract_all(poem, "[[:upper:]]")

然后我取消列出poem_cap:

one_word <- unlist(poem_cap)
one_word

下一个合乎逻辑的步骤是应用str_c:

The next logical step is to apply str_c:

one_word2 <- str_c(one_word, sep="")

但 R 一直在输出不同的字母！如果我复制 one_word2 的输出，用逗号分隔并将 str_c 应用到输出，它的工作原理:

But R keeps putting out separate letters! If I copy the output of one_word2, separate it with commas and apply str_c to the output, it works:

one_word2 <- str_c("A", "T", "L", "L", "K", "D", "D", "S", "S", "N", "S", "M", "J", "S", "L", "F", sep="")
one_word

为什么会这样?我犯了一个错误吗?如何将 one_word2 转换为我可以使用的 str_c ?

Why does this happen? Is there a mistake I'm making? How do I transform one_word2 into something str_c I can work with?

推荐答案

Base R 方法，您可以简单地在一行中使用 gsub 只保留大写字母和粘贴它们(折叠，如@David Arenburg 下划线所示):

Base R approach, you can simply use gsub in a one liner to keep only capital letters and paste them (with collapse, as @David Arenburg underlined):

paste(gsub('[^A-Z]','',poem), collapse='')
#[1] "ATLLKDDSSNSMJSLF"

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