CODEWITHSUNDEEP
rextractgsub
user6907265
user6907265

Reputation:

Extract Between Parts of a String

I have a string of names in the following format:

names <- c("Q-1234-1", "Q-1234-2", "Q-1234-1-8", "Q-1234-2-8")

I am trying to extract the single digit after the second hyphen. There are instances where there will be a third hyphen and an additional digit at the end of the name. The desired output is: 

1, 2, 1, 2

I assume that I will need to use sub/gsub but am not sure where to start. Any suggestions?

Upvotes: 1

Views: 65

Answers (2)

svenhalvorson
svenhalvorson

Reputation: 1080

Here's an alternative using stringr

library("stringr")
names <- c("Q-1234-1", "Q-1234-2", "Q-1234-1-8", "Q-1234-2-8")
output = str_split_fixed(names, pattern = "-", n = 4)[,3]

Upvotes: 0

akrun
akrun

Reputation: 886938

We can use sub to match the pattern of zero or more characters that are not a - ([^-]*) from the start (^) of the string followed by a - followed by zero or more characters that are not a - followed by a - and the number that follows being captured as a group. In the replacement, we use the backreference of the captured group (\\1)

as.integer(sub("^[^-]*-[^-]*-(\\d).*", "\\1", names))
#[1] 1 2 1 2

Or this can be modified to

as.integer(sub("^([^-]*-){2}(\\d).*", "\\2", names))
#[1] 1 2 1 2

Upvotes: 1

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