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

gsub Remove prefix and suffix:

gsub(".*-|\\.txt$", "", x)

tools package Use file_path_sans_ext from tools to remove extension and then use sub to remove prefix:

library(tools)
sub(".*-", "", file_path_sans_ext(x))

strapplyc Extract the digits after - and before dot. See gsubfn home page for more info:

library(gsubfn)
strapplyc(x, "-(\\d+)\\.", simplify = TRUE)

Note that if it were desired to return a numeric we could use strapply rather than strapplyc like this:

strapply(x, "-(\\d+)\\.", as.numeric, simplify = TRUE)