检查字符串是只包含数字还是只包含字符(R)

Question

我有这三个字符串：

letters <- "abc" 
numbers <- "123" 
mix <- "b1dd"

我如何检查这些字符串中哪一个只包含字母还是只包含数字（用R表示）？

字母只能在字母检查中为TRUE

grepl("[A-Za-z]", letters) 

它对字母很有效，但对混合也很有效，这是我不想要的。

提前谢了。

Answer 1

# Check that it doesn't match any non-letter
letters_only <- function(x) !grepl("[^A-Za-z]", x)

# Check that it doesn't match any non-number
numbers_only <- function(x) !grepl("\\D", x)

letters <- "abc" 
numbers <- "123" 
mix <- "b1dd"

letters_only(letters)
## [1] TRUE

letters_only(numbers)
## [1] FALSE

letters_only(mix)
## [1] FALSE

numbers_only(letters)
## [1] FALSE

numbers_only(numbers)
## [1] TRUE

numbers_only(mix)
## [1] FALSE