r - 如何将列表中的字符(0)转换为 NA？

Question

怎么可以character(0)转换为 NA在列表中？
例子:

a = list("a", character(0), "b", "c")

到

a = list("a", NA, "b", "c")

Answer 1

替换 character(0)仅(假设您的意思是 character(0) 而不是 "character(0)" ):

a = list("a", character(0), "b", "c")

lapply(a, function(x) if(identical(x, character(0))) NA_character_ else x)

#[[1]]
#[1] "a"

#[[2]]
#[1] NA

#[[3]]
#[1] "b"

#[[4]]
#[1] "c"

替换所有长度为 0 的元素:

a[lengths(a) == 0] <- NA_character_

a
#[[1]]
#[1] "a"

#[[2]]
#[1] NA

#[[3]]
#[1] "b"

#[[4]]
#[1] "c"