R/shuffle_with_blocks.R

In grebbel/formr_test: formr survey framework

#' Generate a order for elements that is shuffled in blocks
#'
#' The resulting order preserves the original order, but shuffles (a)
#' equal numeric entries (11, 11, 11) among each other and (b) shuffles
#' equal letter entries ('A', 'A', 'B', 'B') in blocks so that the order
#' within the letter is preserved, but the letters are randomly ordered.
#'
#' @param desired_order alphanumeric vector consisting of natural numbers and letters
#' @export
#' @examples
#' desired_order = c(1,2,3,4,5,'A','A','B','B',10,11,11,11,11,15,16,17)
#' shuffleWithBlocks(desired_order)

shuffleWithBlocks = function(desired_order) {
  block_pos = which(tolower(stringr::str_sub(desired_order, 
    1, 1)) %in% letters)  ## find blocks
  blocks = unique(desired_order[block_pos])  ## unique letters
  real_order = 1:length(desired_order)  ## determine the order they were in the item table
  
  block_order = stats::runif(length(blocks), utils::head(block_pos, 1), (utils::head(block_pos, 
    1) + 1))  ## get a uniform dist of random numbers from the first block position. this solution ignores multiple blocks.
  
  resulting_order = desired_order
  for (i in 1:length(blocks)) {
    ## loop through blocks
    resulting_order[resulting_order == blocks[i]] = block_order[i]  ## replace the block letter with its assigned number.
  }
  
  resulting_order = as.numeric(resulting_order)
  resulting_order[-block_pos] = resulting_order[-block_pos] + 
    stats::runif(length(resulting_order[-block_pos]), 0.01, 0.99)  ### now shuffle all elements which have an equal number
  
  order(resulting_order, real_order)
}