Replace part of string with mutate (in a pipe)

Here is one way using str_sub<- in a pipe.

d %>%
  mutate(txt = `str_sub<-`(txt, 3, 6, value = repl))
## A tibble: 3 x 2
#  txt            repl 
#  <chr>          <chr>
#1 i_1111_GES     1111 
#2 i_1111_OISO    1111 
#3 i_2222_ASE1333 2222 

Note that argument value is the last, so it must be passed assigned to its name.

d %>% 
  mutate(txt = str_replace(txt, '0000', repl))

Though probably it will be better with a regex instead of '0000'.

You can probably do:

d %>%
 mutate(txt = str_replace(txt, str_sub(txt, 3, 6), repl))

  txt            repl 
  <chr>          <chr>
1 i_1111_GES     1111 
2 i_1111_OISO    1111 
3 i_2222_ASE1333 2222

Here you first substring and then replace this substring with repl.

Or:

d %>%
 mutate(txt = {str_sub(txt, 3, 6) <- repl; txt})