r - R 中的 grepl 查找与任何字符串列表的匹配项

Question

在引用值列表时是否可以使用 grepl 参数，也许使用 %in% 运算符？我想获取下面的数据，如果动物名称中有“狗”或“猫”，我想返回某个值，比如“保持”；如果它没有“狗”或“猫”，我想返回“丢弃”。

data <- data.frame(animal = sample(c("cat","dog","bird", 'doggy','kittycat'), 50, replace = T))

现在，如果我只是通过严格匹配值来做到这一点，比如“猫”和“狗”，我可以使用以下方法:

matches <- c("cat","dog")

data$keep <- ifelse(data$animal %in% matches, "Keep", "Discard")

但是使用 grep 或 grepl 仅指列表中的第一个参数:

data$keep <- ifelse(grepl(matches, data$animal), "Keep","Discard")

返回

Warning message:
In grepl(matches, data$animal) :
  argument 'pattern' has length > 1 and only the first element will be used

请注意，我在搜索中看到了这个线程，但这似乎不起作用:
grep using a character vector with multiple patterns

Answer 1

您可以在 | 的正则表达式中使用“或”( grepl )语句.

ifelse(grepl("dog|cat", data$animal), "keep", "discard")
# [1] "keep"    "keep"    "discard" "keep"    "keep"    "keep"    "keep"    "discard"
# [9] "keep"    "keep"    "keep"    "keep"    "keep"    "keep"    "discard" "keep"   
#[17] "discard" "keep"    "keep"    "discard" "keep"    "keep"    "discard" "keep"   
#[25] "keep"    "keep"    "keep"    "keep"    "keep"    "keep"    "keep"    "keep"   
#[33] "keep"    "discard" "keep"    "discard" "keep"    "discard" "keep"    "keep"   
#[41] "keep"    "keep"    "keep"    "keep"    "keep"    "keep"    "keep"    "keep"   
#[49] "keep"    "discard"

正则表达式 dog|cat告诉正则表达式引擎查找 "dog"或 "cat" ，并返回两者的匹配项。