R manipulate strings to make a certain length

Question

I have a list of numbers (used as characters), for instance,

IDs <- as.character(c('0', '01', '002'))

that I would like to add '0's to, to make so that they all have the same number of characters (3). How can I do this?

IDs2 <- c('000', '001', '002')

Answer 1

You can use stringr::str_pad:

library(stringr)
IDs <- as.character(c('0', '01', '002')) 

str_pad(IDs, width = 3, pad = '0')
# [1] "000" "001" "002"

Or use sprintf:

sprintf('%03s', IDs)
# [1] "000" "001" "002"