R/mark_dist.R

In debruine/markr: University of Glasgow INP/Psych Marking

#' Marking Distribution Graph
#'
#' \code{mark_dist} create a graph of the marking distribution
#'
#' @param marking list containing a dataframe (marks)
#' @param by facet graphs by question or marker (default FALSE)
#' 
#' @return ggplot
#' @examples
#' mark_dist(marking_example)
#' @export

mark_dist <- function(marking, by = FALSE) {
  if (is.list(marking)) {
    mark_table <- marking$marks
  } else if (is.data.frame(marking)) {
    mark_table <- marking
  } else {
    stop("The first argument must be a dataframe 
         or list with the data in `marks`.")
  }
  
  md <- mark_table %>%
    dplyr::filter(!is.na(mark)) %>%
    ggplot2::ggplot() +
    ggplot2::geom_histogram(
      ggplot2::aes(mark, fill = as.factor(mark)), 
      binwidth = 1, 
      color = "white"
    ) +
    ggplot2::scale_fill_manual(
      values = viridis::viridis(23, 0.75), 
      limits = 0:22, 
      guide = "none"
    ) +
    ggplot2::scale_x_continuous(
      breaks=seq(0,22,2), 
      limits = c(-0.5, 22.5)
    ) +
    ggplot2::theme_minimal() 
  
  if (by == "question") {
    md + ggplot2::facet_grid(gsub("^(Q)(\\d{1})$", "\\10\\2", question)~.)
  } else if (by == "marker") {
    md + ggplot2::facet_grid(marker~.)
  } else {
    md
  }
}