R/OA2LHD.R

In LHD: Latin Hypercube Designs (LHDs)

#' Transfer an Orthogonal Array (OA) into an LHD
#'
#' \code{OA2LHD} transfers an OA into an LHD with corresponding size
#'
#' @param OA An orthogonal array matrix.
#'
#' @return If the input is logical, then the output will be an LHD whose sizes are the same as input OA. The assumption is that the elements of OAs must be positive.
#'
#' @references Tang, B. (1993) Orthogonal-array-based latin hypercubes. \emph{Journal of the Americal Statistical Association}, \strong{88}, 1392-1397.
#'
#' @examples
#' #create an OA(9,2,3,2)
#' OA=matrix(c(rep(1:3,each=3),rep(1:3,times=3)),ncol=2,nrow=9,byrow = FALSE);OA
#'
#' #Transfer the "OA" above into a LHD according to Tang (1993)
#' tryOA=OA2LHD(OA)
#' OA;tryOA
#' @export


OA2LHD=function(OA){
  n=dim(OA)[1]
  m=dim(OA)[2]
  s=length(unique(OA[,1]))

  #OA: OA must be an orthogonal array
  #n: number of rows of OA
  #m: number of columns of OA
  #s: number of levels of OA
  LHD=OA

  #Create a 3-dimentional array named k, which corresponds to k=1,2,...,s
  k=rep(0,n)
  dim(k)=c(n/s,1,s)

  for (j in 1:m) {
    for (i in 1:s) {
      k[,,i]=seq(from=(i-1)*n/s+1,to=(i-1)*n/s+n/s,1) #This is the formula from Tang (1993)
      k[,,i]=sample(k[,,i])

      LHD[,j][LHD[,j]==i]=k[,,i]*100

    }

  }
  LHD=LHD/100
  LHD
}