Extract a number from a string in r

Question

Hello how can I extract a number that is between two dashes from a text?

Here is an exampledataset:

text.var <- c("abd-GEN-eft-na-M-D-BINED-10-XX1","abd-GEN-eft-na-M-D-BINED-2-XX2","abd-GEN-eft-na-M-D-BINED-3-XX1")
id <- c(1,2,3)

data <- data.frame("id"=id,"text"=text.var)

> data
  id                            text
1  1 abd-DEF-eft-na-M-D-BINED-10-XX1
2  2  abd-DEF-eft-na-M-D-BINED-2-XX2
3  3  abd-DEF-eft-na-M-D-BINED-3-XX1

I would like to extract the number between "-"s. My desired outcome would be:

> data
  id                            text    number
1  1 abd-DEF-eft-na-M-D-BINED-10-XX1      10
2  2  abd-DEF-eft-na-M-D-BINED-2-XX2       2
3  3  abd-DEF-eft-na-M-D-BINED-3-XX1       3

Can anyone give some hint?

Thanks

Answer 1

You can use the str_extract function from the "stringr" package:

library(stringr)
str_extract(text.var, "(?<=-)[0-9]+(?=-)")

The (?<= ) and (?= ) are the string look behind and look ahead options.

Answer 2

You can do this with sub and a regular expression.

text.var <- c("abd-GEN-eft-na-M-D-BINED-10-XX1","abd-GEN-eft-na-M-D-BINED-2-XX2","abd-GEN-eft-na-M-D-BINED-3-XX1")
id <- c(1,2,3)
number = as.numeric(sub(".*-(\\d+)-.*", "\\1", text.var))

data <- data.frame("id"=id,"text"=text.var, number)

data
 id                            text number
1  1 abd-GEN-eft-na-M-D-BINED-10-XX1     10
2  2  abd-GEN-eft-na-M-D-BINED-2-XX2      2
3  3  abd-GEN-eft-na-M-D-BINED-3-XX1      3

A little extra detail

In the regular expression, -\\d+- picks out a sequence of digits surrounded by dashes. I put parentheses around the \d part to store the digits found to get -(\\d+)- . .* before and after -(\\d+)- match all the rest of the characters. So sub will replace the entire string with just the digits. That gives strings with the digits. I used as.numeric to make these into numbers rather than strings.

Answer 3

We can use str_extract

library(stringr)
library(dplyr)
data %>% 
   mutate(number = as.numeric(str_extract(text, "\\d+(?=-)")))
#    id                            text number
#1  1 abd-GEN-eft-na-M-D-BINED-10-XX1     10
#2  2  abd-GEN-eft-na-M-D-BINED-2-XX2      2
#3  3  abd-GEN-eft-na-M-D-BINED-3-XX1      3