partial_credit_contour_plot: Generate contour plot for partial credit analysis
Description
The contour plot is for sensitivity analysis. Currently it supports given DOOR
outcome categories of three or four. The contour plot assigns every combinations
of grade keys given a DOOR outcome distribution
Numeric vectors of DOOR proportion or frequency distribution for group 1, group 2.
The entries should be ordered from most desirable to least desirable
n1, n2
Sample sizes of group 1, group 2; must be specified if method = "prop"
summary_obj
An object returned by individual_to_summary(); Alternative
input for y1 and y2
data_type
Either "freq" for frequency input or "prop" for proportion input
when using y1 and y2