将字符串 'NULL' 替换为 NA

Question

大多数搜索结果给了我相反的结果，将 NULL 或 NA 转换为字符串“NA”。我不希望这样，我想将“NULL”的字符串实例转换为 NA，但收到错误:

bla <- c('foo', 'bar', NA, 'NULL')

str_replace_all(bla, 'NULL', NA)
Error: `replacement` must be a character vector

还尝试过:

str_replace_all(bla, 'NULL', NA_real_)
Error: `replacement` must be a character vector

如何将 bla 中的 'NULL' 情况转换为 NA？

[编辑]

明确地说，我实际上是在 dplyr 链中执行此操作，例如

bla <- data.frame(s = c('foo', 'bar', NA, 'NULL'), n = 1:4 )
> bla
     s n
1  foo 1
2  bar 2
3 <NA> 3
4 NULL 4
> bla %>% mutate(s = str_replace_all(bla, 'NULL', NA_real_))
Error: Problem with `mutate()` input `s`.
x `replacement` must be a character vector
ℹ Input `s` is `str_replace_all(bla, "NULL", NA_real_)`.

Answer 1

只需使用 == 而不是正则表达式子字符串替换

bla[bla == "NULL"] <- NA

-输出

bla
[1] "foo" "bar" NA    NA   

---

使用str_replace/str_replace_all，为NA指定正确的类型(默认情况下，NA是逻辑的，这会与原始向量类型

根据？NA

NA is a logical constant of length 1 which contains a missing value indicator. NA can be coerced to any other vector type except raw. There are also constants NA_integer_, NA_real_, NA_complex_ and NA_character_ of the other atomic vector types which support missing values: all of these are reserved words in the R language.

str_replace_all(bla, 'NULL', NA_character_)
[1] "foo" "bar" NA    NA   

此外，str_replace主要用于子字符串替换，而不是用于固定的完整字符串替换(因为我们也可能会发现效率下降)

---

在tidyverse中，还有na_if

library(dplyr)
bla %>% 
    mutate(s = na_if(s, "NULL"))
     s n
1  foo 1
2  bar 2
3 <NA> 3
4 <NA> 4