Plot Discrimination Index vs Difficulty Index

Plots discrimination index, as calculated using the "conventional" formula, or via "PBCC", against difficulty index. Several parameters control settings related to the appearance of the final plot.

plotDiscriminationDifficulty(mctd, type = "conventional",
  show_labels = TRUE, hide_legend = TRUE, show_guidelines = TRUE,
  show_gridlines = TRUE, max_limits = "max_x")

Arguments

mctd	Existing mcTestAnalysis data object
type	One of "conventional", "pbcc", or "pbcc_modified"
show_labels	Should the question number be shown next to points? If ggrepel is installed it will be used to ensure that all point labels are legible on the plot.
hide_legend	Should the plot legend be hidden?
show_guidelines	Should recomended discrimination or difficulty indice ranges be shown on the plot as a dotted line?
show_gridlines	Should the plot include gridlines?
max_limits	Set x- and y-axis limits. One of "max_x" (x positive, y free), "max_y" (x free, y positive), "max_y+" (x free, y in [-1,1]), "max_all+" (x positive, y positive), "max_all" (x positive, y in [-1,1]), and NULL (all free).