使用正则表达式从R中的字符串中提取数字

Question

I have a string like this:

myString <- "[0.15][4577896]blahblahblahblahwhatever"

I need to extract the number between second brackets.

Currently I am trying to use this:

str_extract(myString, "\\]\\[(\\d+)")

But this gives me ][4577896

My desired result would be: 4577896

How could I achieve this?

Answer 1

With no need of look behinds

gsub(".*\\[(\\d+).*","\\1",myString)
[1] "4577896"

Answer 2

You can try this . (?<=\\]\\[)(\\d+)

This is a demo. https://regex101.com/r/fvHW05/1

Answer 3

Here is another version with minimal or no regex

qdapRegex::ex_between_multiple(myString, "[", "]")[[2]]
#[1] "4577896"

It extracts all the substring between [ and ] and we select the value between second bracket. You can convert it into numeric or integer if needed.

Answer 4

You may use

^(?:[^\[\]]*\[[^\[\]]+\])[^\]\[]*\[([^\]\[]+).+

And replace this with the first captured group using gsub , see a demo on regex101.com . In base R :

myString <- "[0.15][4577896]blahblahblahblahwhatever"

pattern <- "^(?:[^\\[\\]]*\\[[^\\[\\]]+\\])[^\\]\\[]*\\[([^\\]\\[]+).+"
gsub(pattern, "\\1", myString, perl = T)
# [1] "4577896"

Answer 5

An option using str_extract

library(stringr)
str_extract(myString, "(?<=.\\[)([0-9]+)")
#[1] "4577896"