#' Unscales a scaled data.frame

#'

#' \code{unscale} is a generic function that unscale and/or uncenter the columns

#' of a matrix generated by the scale base function

#'

#' @param x A numeric matrix.

#'

#' @return

#' Return a matrix, uncenterd and unscaled. Attributes "scaled:center" and

#' "scaled:scale" are removed.

#'

#'

#' @details

#' \code{unscale} uses attributes added by the scale function "scaled:scale" and

#' "scaled:center" and use these scaling factor to retrieve the initial matrix.

#' It first unscales and then uncenters.

#'

#'

#' @seealso \code{\link[base]{scale}}

#'

#' @examples

#' X <- matrix(1:9, ncol = 3)

#' X.scale <- scale(X, center = TRUE, scale = TRUE)

#' X.unscale <- unscale(X.scale)

#' all(X == X.unscale)

#'

#' @export

unscale <- function(x){

    stopifnot(is(x, "matrix"))

    attrib <- attributes(x)

    if("scaled:scale" %in% names(attrib)){

        x  <- x * attrib$`scaled:scale`

        attr(x, "scaled:scale") <- NULL

    }

    if("scaled:center" %in% names(attrib)){

        x <- x + matrix(rep(attrib$`scaled:center`,

                            each = nrow(x)), nrow = nrow(x))

        attr(x, "scaled:center") <- NULL

    }

    return(x)

}