R/UniqueSeq.R

In SSBtools: Statistics Norway's Miscellaneous Tools

#' Sequence within unique values 
#'
#' @param x vector 
#' @param sortdata matrix or vector to determine sequence order
#'
#' @return integer vector
#' @export
#' @author Øyvind Langsrud
#'
#' @examples
#' # 1:4 within A and 1:2 within B
#' UniqueSeq(c("A", "A", "B", "B", "A", "A"))
#' 
#' # Ordered differently
#' UniqueSeq(c("A", "A", "B", "B", "A", "A"), c(4, 5, 20, 10, 3, 0))
UniqueSeq <- function(x, sortdata = matrix(1L, length(x), 0)) {
  ix <- SortRows(cbind(x, sortdata), index.return = TRUE)
  nr <- seq_len(length(x))
  sortx <- x[ix]
  (1L + nr - nr[match(sortx, sortx)])[order(ix)]
}