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Check if row contains ONLY NUMBERS or ONLY CHARACTERS (R)

I have these three lines:

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

How can I check which of these lines contains ONLY LETTERS or ONLY NUMBERS (in R)?

letters

must be TRUE only in LETTERS

numbers

must be TRUE in checking NUMBERS ONLY

mix

must be FALSE in any situation

I've tried several approaches now, but none of them really worked for me :(

For example, if I use

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

This works well for letters

, but it also works for mix

which I don't want.

Thank you in advance.

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2 answers


you need to keep your regex



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
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# 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


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