检查字符串是否仅包含数字或仅包含字符（R）

Question

我有这三个字符串：

letters

如何检查这些字符串中的哪一个仅包含字母或仅包含数字（在R中）？

numbers只应在LETTERS ONLY中检查

mix只应在NUMBERS ONLY检查

中为TRUE

grepl("[A-Za-z]", letters) 在任何情况下都应该是假的

我现在尝试了几种方法，但它们中没有一种对我有效:(

例如，如果我使用

letters

它适用于mix，但它也适用于.git/hooks/pre-commit，我不想要的。

提前致谢。

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

Answer 2

你需要坚持你的正则表达式

all_num <- "123"
all_letters <- "abc"
mixed <- "123abc"


grepl("^[A-Za-z]+$", all_num, perl = T) #will be false
grepl("^[A-Za-z]+$", all_letter, perl = T) #will be true
grepl("^[A-Za-z]+$", mixed, perl=T) #will be false

Answer 3

使用 stringr 包

library(stringr)
all_num <- "123"
all_letters <- "abc"
mixed <- "123abc"

# LETTERS ONLY
str_detect(all_num, "^[:alpha:]+$")
str_detect(all_letters, "^[:alpha:]+$")
str_detect(mixed, "^[:alpha:]+$")

# NUMBERS ONLY
str_detect(all_num, "^[:digit:]+$")
str_detect(all_letters, "^[:digit:]+$")
str_detect(mixed, "^[:digit:]+$")