In R, I'm looking for a way to add a specific character to all values in a column of a data frame based on the number of characters. Put it simply: if cell has 4 characters, do nothing. If a cell has 3 characters, add a 0 in front of every cell value. Every cell value has either 3 or 4 characters.
id <- c(1000, 2000, 300, 400, 5000, 600)
df <- data.frame(id)
#Desired Result (df)
#id
#1000
#2000
#0300
#0400
#5000
#0600
