Extract numeric part of strings of mixed numbers and characters in R

Question

I have a lot of strings, and each of which tends to have the following format: Ab_Cd-001234.txt I want to replace it with 001234. How can I achieve

Answer 1

Using gsub or sub you can do this :

 gsub('.*-([0-9]+).*','\\1','Ab_Cd-001234.txt')
"001234"

you can use regexpr with regmatches

m <- gregexpr('[0-9]+','Ab_Cd-001234.txt')
regmatches('Ab_Cd-001234.txt',m)
"001234"

EDIT the 2 methods are vectorized and works for a vector of strings.

x <- c('Ab_Cd-001234.txt','Ab_Cd-001234.txt')
sub('.*-([0-9]+).*','\\1',x)
"001234" "001234"

 m <- gregexpr('[0-9]+',x)
> regmatches(x,m)
[[1]]
[1] "001234"

[[2]]
[1] "001234"