R/transmat.R

In soodoku/guess: Adjust Estimates of Learning for Guessing

#' transmat: Cross-wave transition matrix
#'
#' @description Prints Cross-wave transition matrix and returns the vector behind the matrix.  
#' Missing values are treated as ignorance. Don't know responses need to be coded as 'd'.
#' @param pre_test_var Required. A vector carrying pre-test scores of a particular item. Only 
#' @param pst_test_var Required. A vector carrying post-test scores of a particular item
#' @param subgroup     Optional. A Boolean vector indicating rows of the relevant subset.  
#' @param force9       Optional. There are cases where DK data doesn't have DK. But we need the entire matrix. By default it is FALSE.
#' @return a numeric vector. 
#' Assume 1 denotes correct answer, 0 and NA incorrect, and d 'don't know.'
#' When there is no don't know option and no missing, the entries are: x00, x10, x01, x11
#' When there is a don't know option, the entries of the vector are: x00, x10, xd0, x01, x11, xd1, xd0, x1d, xdd
#' @export
#' @examples
#' pre_test_var <- c(1,0,0,1,0,1,0)
#' pst_test_var <- c(1,0,1,1,0,1,1)
#' transmat(pre_test_var, pst_test_var)
#' 
#' # With NAs
#' pre_test_var <- c(1,0,0,1,"d","d",0,1,NA)
#' pst_test_var <- c(1,NA,1,"d",1,0,1,1,"d") 
#' transmat(pre_test_var, pst_test_var)

transmat <- function(pre_test_var, pst_test_var, subgroup = NULL,
                    force9 = FALSE) {

  if ( !is.null(subgroup)) {

    pre_test_var <- subset(pre_test_var, subgroup)
    pst_test_var <- subset(pst_test_var, subgroup)
  }

  # No NAs
  pre_test_nona <- nona(as.character(pre_test_var))
  pst_test_nona <- nona(as.character(pst_test_var))

  # Check if the vector has only one of the 4 values
  if (!all(unique(c(pre_test_nona, pst_test_nona)) %in% c(NA, "1", "0", "d"))) {
    stop("The input vectors can only contain: 0, 1, NA, d")
  }

  pre_pst <- paste0(pre_test_nona, pst_test_nona)

  # Get the numbers
  x00     <- sum(pre_pst == "00")
  x10     <- sum(pre_pst == "10")
  x01     <- sum(pre_pst == "01")
  x11     <- sum(pre_pst == "11")
  xd0     <- sum(pre_pst == "d0")
  xd1     <- sum(pre_pst == "d1")
  x1d     <- sum(pre_pst == "1d")
  xdd     <- sum(pre_pst == "dd")
  x0d     <- sum(pre_pst == "0d")

  res <- c(x00, x01, x10, x11)
  names(res) <- c("x00", "x01", "x10", "x11")

  if ( (xd0 + xd1 + x1d + xdd != 0) | force9) {

    res <- c(x00, x01, x0d, x10, x11, x1d, xd0, xd1, xdd)
    names(res) <- c("x00", "x01", "x0d", "x10", "x11", "x1d",
                    "xd0", "xd1", "xdd")
  }
  return(invisible(res))
}