get_tau {dscore}

Obtain difficulty parameters from item bank

Description

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

Usage

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. Name of the key that bundles the difficulty estimates pertaining one the same Rasch model. View builtin_keys for an overview of the available keys.

itembank

A data.frame with at least two columns named 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(s)

Stef van Buuren 2020

See Also

builtin_itembank(), dscore()

Examples

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