InsertastringbyconditioninR

I have this situation, but with much more information:

Barcode
NM00000512
NM000522
NM00000513
NM000514

And I would like to insert two more zeros in the shorter Barcodes, like this:

Barcode
NM00000512
NM00000522
NM00000513
NM00000514

I tried this df$Barcode <- gsub('NM000', "NM00000",df$Barcode) but didn't work. Thanks

Other answers make assumptions about the number of zeros (that there should be five). I assume that there should be exactly two characters in the front. If that's not the case, you could modify it to split the string before the first numeric digit (or according to whatever different rule applies).

barcode <- c("NM00000512", "NM000522", "NM00000513", "NM000514")


pad <- function(barcode) {
  x <- as.integer(substring(barcode, 3)) #extract numbers
  n <- max(nchar(barcode)) - 2 #desired length of number in string
  paste0(substring(barcode, 1, 2), #the two characters
         sprintf(paste0("%0", n, "i"), x) #pad with zeros
         )
}

pad(barcode)
#[1] "NM00000512" "NM00000522" "NM00000513" "NM00000514"