Remove pattern from string with gsub

Question

I am struggling to remove the substring before the underscore in my string. I want to use * (wildcard) as the bit before the underscore can vary:

a <- c("foo_5", "bar_7")

a <- gsub("*_", "", a, perl = TRUE)

The result should look like:

> a
[1] 5 7

I also tried stuff like "^*" or "?" but did not really work.

score 59 · Accepted Answer · answered Aug 02 '12 at 11:19

59

The following code works on your example :

gsub(".*_", "", a)

answered Aug 02 '12 at 11:19

Pop

great thanks. What does the '.' stands for? Why does the star "*" (wildcard) does not work by its own? I don't understand? – user969113 Aug 02 '12 at 11:20
4

'.' stands for any character, so that ".*" stands for any number of any character. You can find more explanations by typing `?regex`. – Pop Aug 02 '12 at 11:23
1

Ah I see! I thought * includes the meaning of the '.' already! Well, now I know better. thanks again! – user969113 Aug 02 '12 at 13:51
1

For clarification, you are confusing the regular expression (regex) syntax with glob syntax; both use the * star character as a wild card, but it means slightly different things between the two. – user5359531 Apr 29 '16 at 02:44

score 8 · Answer 2 · answered Apr 09 '16 at 20:20

8

Alternatively, you can also try:

gsub("\\S+_", "", a)

answered Apr 09 '16 at 20:20

Madhu Sareen

score 2 · Answer 3 · answered Jun 02 '20 at 18:43

2

Just to point out that there is an approach using functions from the tidyverse, which I find more readable than gsub:

a %>% stringr::str_remove(pattern = ".*_")

answered Jun 02 '20 at 18:43

elcortegano

a is a vector not a dataframe. This would result in the following error: 'Warning message: In stri_replace_first_regex(string, pattern, fix_replacement(replacement), : argument is not an atomic vector; coercing" – Colin McGovern Mar 09 '22 at 20:00

score -2 · Answer 4 · edited Jul 23 '17 at 03:54

-2

as.numeric(gsub(pattern=".*_", replacement = '', a)
[1] 5 7

edited Jul 23 '17 at 03:54

Nathan Tuggy

answered Jul 23 '17 at 03:08

Praveen

2

Always add explanation to your answer besides the code for better understanding – bigbounty Jul 23 '17 at 04:40

4 Answers4