我正在尝试获取一个包含大量段落的表达式，并在该行中找到两个特定单词的行，所以我正在寻找 AND 运算符？有什么办法可以做到这一点？
例如：
c <- ("She sold seashells by the seashore, and she had a great time while doing so.")
我想要一个表达式，它可以找到一行中同时包含“sold”和“great”的行。
我尝试过类似的方法：
grep("sold", "great", c, value = TRUE)
有什么想法吗？
非常感谢！
【问题讨论】：
标签： r regex operator-keyword operations
您可以创建两个捕获组，假设单词的顺序不重要
grep("(sold|great)(?:.+)(sold|great)", c, value = TRUE)
【讨论】：
虽然在大多数情况下，我会使用 stringr 包，正如 CPak 的回答中已经建议的那样，我也有 grep 解决方案：
# create the sample string
c <- ("She sold seashells by the seashore, and she had a great time while doing so.")
# match any sold and great string within the text
# ignore case so that Sold and Great are also matched
grep("(sold.*great|great.*sold)", c, value = TRUE, ignore.case = TRUE)
嗯，还不错吧？但是如果有一个词只包含短语sold 或great 呢？
# set up alternative string
d <- ("She saw soldier eating seashells by the seashore, and she had a great time while doing so.")
# even soldier is matched here:
grep("(sold.*great|great.*sold)", d, value = TRUE, ignore.case = TRUE)
所以你可能想要使用单词边界，即匹配整个单词：
# \\b is a special character which matches word endings
grep("(\\bsold\\b.*\\bgreat\\b|\\bgreat\\b.*\\bsold\\b)", d, value = TRUE, ignore.case = TRUE)
\\b 匹配字符串中的第一个字符、字符串中的最后一个字符或两个字符之间，其中一个属于单词，另一个不属于：
更多关于 \b 元字符的信息在这里：
http://www.regular-expressions.info/wordboundaries.html
【讨论】：
重复的帖子可能会让您入门，但我认为不能直接解决您的问题。
您可以将stringr::str_detect 与all 结合使用
pos <- ("She sold seashells by the seashore, and she had a great time while doing so.") # contains sold and great
neg <- ("She bought seashells by the seashore, and she had a great time while doing so.") # contains great
pattern <- c("sold", "great")
library(stringr)
all(str_detect(pos,pattern))
# [1] TRUE
all(str_detect(neg,pattern))
# [1] FALSE
stringr::detect 具有搜索模式字符向量的优势（优于 grepl）
【讨论】：