在特殊字符之间提取文本R.

Question

I have multiple strings as shown below:

filename="numbers [www.imagesplitter.net]-0-0.jpeg"
filename1="numbers [www.imagesplitter.net]-0-1.jpeg"
filename2="numbers [www.imagesplitter.net]-19-9.jpeg"

I want the text that appears between the second "-" and the last period. I would like to get 0,1,9 respectively.

How do I do this? I am not sure how to detect the second "-" and the last period.

Answer 1

Try

sub('^[^-]*-[^-]*-(\\d+)\\..*$', '\\1', files)
#[1] "0" "1" "9"

or

 gsub('^[^-]*-[^-]*-|\\..*$', '', files)
 #[1] "0" "1" "9"

data

files <- c(filename, filename1, filename2)

Answer 2

Try this:

files=c(filename, filename1, filename2)

sub(".*-(.+)\\.jpeg", "\\1", files)

Answer 3

You could use regmatches function also.

> x <- c("numbers [www.imagesplitter.net]-0-0.jpeg","numbers [www.imagesplitter.net]-0-1.jpeg", "numbers [www.imagesplitter.net]-19-9.jpeg")
> unlist(regmatches(x, gregexpr("^(?:[^-]*-){2}\\K.*(?=\\.)", x, perl=TRUE)))
[1] "0" "1" "9"

You could use the same regex in stringr , str_extract_all function also.

> library(stringr)
> unlist(str_extract_all(x, perl("^(?:[^-]*-){2}\\K.*(?=\\.)")))
[1] "0" "1" "9"

OR

> unlist(str_extract_all(x, perl("(?<=-)[^-.]*(?=\\.)")))
[1] "0" "1" "9"

OR

> unlist(str_extract_all(x, perl(".*-\\K\\d+")))
[1] "0" "1" "9"

Answer 4

I would simply use strsplit to split the strings accordingly here:

sapply(strsplit(files, '[-.]'), '[', 5)
# [1] "0" "1" "9"

Answer 5

you can try

sub("^[^-]+-[^-]+-(.*)\\.[^\\.]*$", "\\1", c(filename, filename1, filename2))
[1] "0" "1" "9"