R/transform.R

In josephsdavid/tswgewrapped: Helpful wrappers for 'tswge', 'vars' and 'nnfor' time series packages

#' Time Series transformation 
#' @param type either aruma/seasonal or arima, type of transformation to make
#' @param x the time series
#' @param n the order of transformation
#' @return the transformed time series
#' @export
difference <- function(type, x, n){
  szn_trans <- function(x,n){
    tswge::artrans.wge(x, phi.tr = c(rep(0, n - 1), 1))
  }
  arima_trans <- function(x, n) {
    f <- tswge::artrans.wge(x, phi.tr = 1)
    if (n == 1) {
      res <- f
      return(res)
    } else {
      arima_trans(f, n - 1)
    }
  }
  if(is.character(rlang::enexpr(type)) == F){
    type <- as.character(rlang::enexpr(type))
  }
  if (type %in% c('arima',"ARIMA","Arima")){
    return((arima_trans(x,n)))
  }
  if (type %in% c('ARUMA','Aruma','aruma','Seasonal','seasonal')){
    szn_trans(x,n)
  }
}