inst/1-B12/ire/Rsource/gen_seasComp.R

In jlivsey/EMsignal:

#' Generate multivariate seasonal component
#'
#' generates a component that is seasonally (12) difference stationary
#'
#' @param n length of series
#' @param Phi seasonal autoregressive parameter
#' @param Sig covariance martrix white noise component
#' @param burn burn in (defaults to 1000)
#' @param seasonl.period periodicity of component (defaults to 12)
#'
#' @return Ndim x n matrix of observations
#' @export
#'

gen_seasComp = function(n, Phi, Sig, burn=10^3, seasonal.period=12){
  N = n+burn
  Ndim = dim(Sig)[1]

  if(Ndim==1){ # handle univariate case first
    w = rnorm(n = N, mean = 0, sd = sqrt(Sig))
    s = w[1:seasonal.period]
    for(i in (seasonal.period+1):N){
      new.s = -1*sum(s[(i-seasonal.period+1):(i-1)]) + w[i]
      s = c(s, new.s)
    }
    return(s[(burn+1):N])

  } # end of univariate if() statement

  w = rmvnorm(n = N, mean = rep(0,Ndim), sigma = Sig)
  s = w[1:seasonal.period, ]
  for(i in (seasonal.period+1):N){
    new.s = -1*colSums(s[(i-seasonal.period+1):(i-1), ]) + w[i,]
    s = rbind(s, t(new.s))
  }
  return(s[(burn+1):N, ])
}