R/IRT.simulate.R

In TAM: Test Analysis Modules

## File Name: IRT.simulate.R
## File Version: 9.142

#####################################################
# S3 method
IRT.simulate <- function (object, ...) {
  UseMethod("IRT.simulate")
}
#####################################################


######################################################
simulate_mml <- function(object, iIndex=NULL, theta=NULL, nobs=NULL, ...){

  nnodes <- nobs
  A <- object$A
  xsi <- object$xsi$xsi
  B <- object$B
  ndim <- dim(B)[3]
  guess <- object$guess
  maxK <- dim(A)[2]

  if(is.null(iIndex)){
    iIndex <- 1:dim(A)[1]
  }
  nI <- length(iIndex)

  if(is.null(theta)){
    if(is.null(nnodes)){
      nnodes <- nrow(object$person)
    }

    t.mean <- object$beta
    t.sigma <- object$variance
    if(ndim==1){
      theta <- stats::rnorm(nnodes, mean=t.mean, sd=sqrt(t.sigma))
    } else {
      theta <- CDM::CDM_rmvnorm(nnodes, mean=t.mean, sigma=t.sigma)
    }
    theta <-  matrix(theta, ncol=ndim)
  }

  if(is.null(dim(theta)) & ndim==1){
    warning("Theta points should be either NULL or a matrix of same dimensionality as the trait distribution.")
    theta <- matrix(theta, ncol=ndim)

  }
  if(ncol(theta) !=ndim){
    warning("Theta points should be either NULL or a matrix of same dimensionality as the trait distribution.")
    theta <- matrix(theta, ncol=ndim)
  }
  nnodes <- nrow(theta)

  #****
  # calculate probs
  p <- IRT.irfprob(object=class(object), A=A, B=B, xsi=xsi, theta=theta,
                   guess=guess, nnodes=nnodes, iIndex=iIndex, maxK=maxK, ... )

  #****
  # simulate data
  res <- matrix( stats::runif(nnodes * nI), nrow=nnodes, ncol=nI)
  for(ii in 1:nI){
    cat.success.ii <- (res[, ii] > t(apply(p[ii,, ], 2, cumsum)))
    cat.success.ii[is.na(cat.success.ii)] <- FALSE
    res[, ii] <-  c(cat.success.ii %*% rep(1, maxK))
  }

  if ( nrow(object$resp)==nnodes ){
        res[ is.na(object$resp) ] <- NA
  }

  #****
  # Output
  class(res) <- "IRT.simulate"
  return(res)
}

######################################################################
# S3 methods
IRT.simulate.tam.mml <- simulate_mml
IRT.simulate.tam.mml.2pl <- simulate_mml
IRT.simulate.tam.mml.3pl <- simulate_mml
IRT.simulate.tam.mml.mfr <- simulate_mml
######################################################################