irt 0.2.8

Added kappa_coef() function to calculate Cohen’s weighted/unweighted Kappa coefficient.
Response objects prints ‘misc’ fields without an error when there is a factor type variable.
Fixed an error in the function irt:::marginal_reliability(..., method = "empirical").

irt 0.2.6

Plot functions can now suppress plot titles by setting title = NULL.
item_analysis() function now has a new argument stats where only selected item analysis statistics can be calculated.
item_analysis() function can now calculate pval_unadj which is simply the mean of item scores. pval is still the mean of item scores divided by each item’s maximum possible score.
Added area_between_icc() function to calculate the area between two item characteristic curves of two unidimensional dichotomous items. The function can calculate either exact area (except when 3PL with different pseudo-guessing parameters) or area between two theta values.
cat_sim() function can use MAP (maximum-a-posteriori or Bayes Modal) and MAP + ML (i.e. MAP until an imperfect response string and ML after) ability estimation methods.
Responses, items administered, administered item IDs, estimates before or after the administration of an item can be extracted from the individual CAT output. For details, see “?$.cat_output”.
Added output_type argument to est_ability(, output_type = ) function with available following output types: "list", "data.frame", "tibble". Previously, the output was only a “list”.

Bug fix: An Itempool object with one testlet can be printed without an error.
Added $item_ids to testlet object to get the ids of the items within the testlet.
Fixed bugs in plot_empirical_icc() function.

Added $max_score for Testlet objects. For a given Testlet object t1, t1$max_score returns the maximum obtainable score by all items within the testlet.
Added $resp_item_list for Itempool objects. For an Itempool object ip, ip$resp_item_list will combine items that are not in a testlet and items within a testlet and returns a list object that is composed of only Item objects.

Package can be used in MacOS as well. Resolved compiler related issues.
Added est_bilog() function to estimate item parameters for “1PL”, “2PL” and “3PL” models using BILOG-MG on computers with Windows OS. This function requires an installed BILOG-MG program on the machine.