Reputation: 45

10 digit numbers starting with 4 or 6

In R I would like the code to find numbers starting with 4 or 6 in numbers with 10 digits.

This works to get the 10 digit numbers:

grep("^[[:digit:]]{10}$"

This doesn't work to get them starting with 4 or 6:

grep([46]\"^[[:digit:]]{10}$"

Examples

x <- c("4303669792", "6200406014")

Upvotes: 1

Answers (3)

Reputation: 388982

We can use grepl and nchar

grepl("^[4|6]", x) & nchar(x) == 10
#[1]  TRUE  TRUE FALSE FALSE

With grepl find if string starts with "4" or "6" and check if number of characters in it is equal to 10.

If you need the values, subset it

x[grepl("^[4|6]", x) & nchar(x) == 10]
#[1] "4982748923" "6165751984"

data

x <- c('4982748923', '6165751984', '31094583285', '654')

Upvotes: 1

Reputation: 51592

You can use simple math as well, i.e.

x <- c('4982748923', '6165751984', '31094583285')

as.numeric(x) %/% 1000000000 %in% c(4, 6)
#[1]  TRUE  TRUE FALSE

Upvotes: 1

Reputation: 626861

You may use

grep("^[46][0-9]{9}$", x)
       ^^^^      ^

Details

Upvotes: 3