R/nr.R

In mlthom/CogIRT: Cognitive Testing Using Item Response Theory

#-------------------------------------------------------------------------------
#' Newton Raphson Parameter Estimates
#'
#' This function calculates Newton Raphson parameter estimates. It is used
#' mostly for testing.
#'
#' @export nr
#-------------------------------------------------------------------------------

nr <- function(rda = NULL, tol = 1e-9, max_iter = 100, verbose = TRUE) {

  omega_nr <- rda$omega

  fx <- dich_response_deriv(
    y = rda$y,
    nu = rda$nu,
    lambda = rda$lambda,
    kappa = rda$kappa,
    gamma = rda$gamma,
    omega = rda$omega,
    zeta = rda$zeta,
    omega_mu = rda$omega_mu,
    omega_sigma2 = rda$omega_sigma2,
    zeta_mu = rda$zeta_mu,
    zeta_sigma2 = rda$zeta_sigma2
  )

  iter <- 0

  while (any(abs(fx$fpd[[1]]) > tol) && (iter < max_iter)) {

    omega_nr <- omega_nr - fx$fpd[[1]] %*% solve(fx$spd[[1]])

    fx <- dich_response_deriv(
      y = rda$y,
      nu = rda$nu,
      lambda = rda$lambda,
      kappa = rda$kappa,
      gamma = rda$gamma,
      omega = omega_nr,
      zeta = rda$zeta,
      omega_mu = rda$omega_mu,
      omega_sigma2 = rda$omega_sigma2,
      zeta_mu = rda$zeta_mu,
      zeta_sigma2 = rda$zeta_sigma2
    )
    iter <- iter + 1
  }
  if (verbose == TRUE) {
    if (any(abs(fx$fpd[[1]]) > tol)) {
      cat("Algorithm failed to converge\n")
    } else {
      cat("Algorithm converged\n")
    }
  }
  return("omega_nr" = omega_nr)
}