How to remove the last n characters from every element in the R vector

To remove the last n characters from string r, you can use the substr function from the base package as follows:

char_array = c("foo_bar","bar_foo","apple","beer")
> df = data.frame("data"=char_array,"data2"=1:4, stringsAsFactors = FALSE)
> df
     data data2
1 foo_bar     1
2 bar_foo     2
3   apple     3
4    beer     4
df$data = substr(df$data,1,nchar(df$data)-3)
> df  
  data data2
1 foo_     1
2 bar_     2
3   ap     3
4    b     4