Obtain difficulty parameters from item bank

Source: R/get_tau.R

Searches the item bank for matching items, and returns the difficulty estimates. Matching is done by item name. Comparisons are done in lower case.

get_tau(
  items,
  key = NULL,
  itembank = dscore::builtin_itembank,
  verbose = FALSE
)

Arguments

items

A character vector containing names of items to be included into the D-score calculation. Milestone scores are coded numerically as 1 (pass) and 0 (fail). By default, D-score calculation is done on all items found in the data that have a difficulty parameter under the specified key.

key

String. They key identifies 1) the difficulty estimates pertaining to a particular Rasch model, and 2) the prior mean and standard deviation of the prior distribution for calculating the D-score. The default key NULL sets key = "gsed2406". View builtin_keys for an overview of the available keys.

itembank

A data.frame with at least three columns named key, item and tau. By default, the function uses dscore::builtin_itembank. If you specify your own itembank, then you should also provide the relevant transform and qp arguments.

verbose

Logical. Print settings.

Value

A named vector with the difficulty estimate per item with length(items) elements.

Author

Stef van Buuren 2020

Examples

# difficulty levels in the GHAP lexicon
get_tau(items = c("ddifmd001", "DDigmd052", "xyz"))
#> ddifmd001 DDigmd052       xyz 
#>        NA        NA        NA