create string variable from numeric variable with padding 0s

Pad0.R

Pad0 <- function(x, mx=NULL, fill=0) {
  ## pad numeric vars to strings of specified size
  lx <- nchar(as.character(x))
  mx.calc <- max(lx, na.rm=TRUE)
  if (!is.null(mx)) {
    if (mx<mx.calc) {
      stop("number of maxchar is too small")
    }
  } else {
    mx <- mx.calc
  }
  px <- mx-lx
  paste(sapply(px,function(x) paste(rep(fill,x),collapse="")),x,sep="")
  }