Removing characters from a string that contains brackets

[ctheisen]

So I'm trying to figure out how to format my function that grabs my ipaddress to basically just keep the numbers. My function is:

myIPaddress <- readLines("https://lnkd.in/drb3YQZV", warn = FALSE)

The variable is (with the numbers substituted with zeroes so as not to post my actual ip adress)

> myIPaddress
[1] "{\"ip\":\"000.00.000.00\"}"

I want it to be formatted so it just has

> myIPaddress
[1] "000.00.000.00"

I've tried a couple variations of gsub but am struggling. I'm trying to first get rid of everything in the beginning, so I have tried:

> myIPaddress <- readLines("https://lnkd.in/drb3YQZV", warn = FALSE) %>% 
+   gsub(".*\\0",'')
Error in gsub(., ".*\\0", "") : 
  invalid regular expression '{"ip":"000.00.000.00"}', reason 'Invalid contents of {}'
In addition: Warning message:
In gsub(., ".*\\0", "") :
  TRE pattern compilation error 'Invalid contents of {}'

So I think it's having a problem with the fact that some of the characters are in the brackets {}. So I found that I could use the perl=TRUE addition and then it just removed everything, as shown below.

> myIPaddress <- readLines("https://lnkd.in/drb3YQZV", warn = FALSE) %>% 
+   gsub(".*\\1",'',perl=TRUE)
> myIPaddress
[1] ""

So doing it this way just completely removed the whole address. Any help would be appreciated

[W4tRb0y]

Hi,

If I understand the question you can use {stringr} package as per:

library(stringr)

str_extract(myIPaddress, pattern = "\\d.*\\d")

This basically looks for the first and last numbers and extracts everything between them.

Hope this is useful

[ctheisen]

That worked, thanks!

[HanOostdijk]

Maybe this helps ?

myIPaddress<- "{\"ip\":\"000.00.000.00\"}"
(m1 <- gsub("^[^0123456789]+","",myIPaddress))
#> [1] "000.00.000.00\"}"
(m2 <- gsub("\"}$","",m1))
#> [1] "000.00.000.00"
Created on 2022-08-05 by the reprex package (v2.0.1)

[pieterjanvc]

Hello,

I personally think the grep and related functions is base R are very confusing and not intuitive. I recommend you use the "stringr" package from the Tidyverse which is much more elegant.

In your case, you want this:

library(stringr)

str_extract("{\"ip\":\"000.00.000.00\"}", "(\\d+\\.?)+")
#> [1] "000.00.000.00"

^{Created on 2022-08-04 by the reprex package (v2.0.1)}

The regular expression I used looks for the first digit, then keeps adding digits or periods until the full IP address has been extracted.

Hope this helps,
PJ

[andresrcs]

You have to refine the regular expression, also, the stringr package is very handy:

text <- "{\"ip\":\"000.00.000.00\"}"

stringr::str_extract(text, "(\\d{1,3}\\.?){4}")
#> [1] "000.00.000.00"

^{Created on 2022-08-04 by the reprex package (v2.0.1)}

[FJCC]

Try str_extract from the stringr package.

library(stringr)
MyIP <- "{\"ip\":\"000.00.000.00\"}"
str_extract(MyIP, "\\d+\\.\\d+\\.\\d+\\.\\d+")
#> [1] "000.00.000.00"

^{Created on 2022-08-04 by the reprex package (v2.0.1)}

[HanOostdijk]

I feel the need to explain the reason for my "mosterd na de maaltijd" answer:
my answer was the first reaction to the question and I answered that question in terms that the OP used.
My answer was set on hold awaiting clearance by an moderator ??
Later I saw the answer by @W4tRb0y that uses str_extract and indeed I think that is a better solution.
Because my answer was waiting for the moderator, I had the opportunity to delete my solution, but being curious why it was being set for moderation I decided not to do that.
Today my solution was admitted but without giving a reason for the delay.
Still curious why my suggestion was put to moderation. Was it because of the use of gsub?

[andresrcs]

@HanOostdijk

but being curious why it was being set for moderation I decided not to do that.
Today my solution was admitted but without giving a reason for the delay.

It is an auto-flagging system, most likely triggered this time because of the IP-like address used in the example (my answer was auto-flagged too), as far as I know, auto-flags al cleared by a single person (the forum administrator) so sometimes it takes a while depending on his workload.