R - gsub() : trouble when trying to extract a string between ". " and "_"

Question

The R gsub() syntax is so difficult to me ! Could you, please, help me to extract, for example, "DA VINCI" from "16. DA VINCI_RETOUR" ?

I've already tried gsub("_.+$", "", x) but it just removes what is after the "_" and I would like also to remove what is before the ". " !

Thank you so much for your help !

Could you show the failed attempt? It might help you to better understand what went wrong. — NelsonGon, Oct 01 '19 at 15:04
Related, possible duplicate https://stackoverflow.com/q/23518325/680068 — zx8754, Oct 01 '19 at 15:19
I've already seen this post but it didn't help me at all ! Thank you @zx8754 ! — , Oct 01 '19 at 18:39

score 2 · Answer 1 · answered Oct 01 '19 at 15:03

2

Here is one option with capture group to match the pattern of word (\\w+) followed by space and another word as a group and replace with the backreference of the capture group (\\1)

sub("^\\d+\\.\\s+(\\w+\\s+\\w+)_.*", "\\1", str1)

data

str1 <- "16. DA VINCI_RETOUR"

answered Oct 01 '19 at 15:03

akrun

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Thank you very much for your answer ! It works perfectly on "16. DA VINCI_RETOUR" but when I try to use it on an other example like 7. TILLEUL_RETOUR your code doesn't work anymore ! :( – Oct 01 '19 at 15:10
1

@sallyb Please check the pattern you showed int he example and in the new one. IN the first there is `DA` followed by space. In the second one, there is not. regex works with patterns – akrun Oct 01 '19 at 15:11

GKi · Accepted Answer · 2019-10-01T15:23:25.640

2

.* takes everything at the beginning, \\. matches ., (.*) matches everything until and stores it in \\1 _ and .* removes the rest.

x  <- "16. DA VINCI_RETOUR"
sub(".*\\. (.*)_.*", "\\1", x)
#[1] "DA VINCI"

x  <- "7. TILLEUL_RETOUR"
sub(".*\\. (.*)_.*", "\\1", x)
#[1] "TILLEUL"

edited Oct 01 '19 at 15:23

answered Oct 01 '19 at 15:17

GKi

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score 1 · Answer 3 · answered Oct 01 '19 at 15:08

1

An alternative that uses strsplit:

gsub("\\d+\\.\\s","",
      strsplit(the_string,"_")[[1]][1])
[1] "DA VINCI"

Data:

the_string <- "16. DA VINCI_RETOUR"

answered Oct 01 '19 at 15:08

NelsonGon

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R - gsub() : trouble when trying to extract a string between ". " and "_"

3 Answers3

data