How to add leading zeros?

Question

I have a set of data which looks something like this:

anim <- c(25499,25500,25501,25502,25503,25504)
sex  <- c(1,2,2,1,2,1)
wt   <- c(0.8,1.2,1.0,2.         


        

Answer 1

Expanding on @goodside's repsonse:

In some cases you may want to pad a string with zeros (e.g. fips codes or other numeric-like factors). In OSX/Linux:

> sprintf("%05s", "104")
[1] "00104"

But because sprintf() calls the OS's C sprintf() command, discussed here, in Windows 7 you get a different result:

> sprintf("%05s", "104")
[1] "  104"

So on Windows machines the work around is:

> sprintf("%05d", as.numeric("104"))
[1] "00104"

Answer 2

Here's a generalizable base R function:

pad_left <- function(x, len = 1 + max(nchar(x)), char = '0'){

    unlist(lapply(x, function(x) {
        paste0(
            paste(rep(char, len - nchar(x)), collapse = ''),
            x
        )
    }))
}

pad_left(1:100)

I like sprintf but it comes with caveats like:

however the actual implementation will follow the C99 standard and fine details (especially the behaviour under user error) may depend on the platform