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 = "gsed", itembank = dscore::builtin_itembank)

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

A string that sets the key, the set of difficulty estimates from a fitted Rasch model. The built-in keys are: "gsed" (default), "gcdg", and "dutch". Use key = "" to use all item names, which should only be done if there are no duplicate itemnames.

itembank

A data.frame with columns key, item, tau, instrument, domain, mode, number and label. Only columns item and tau are required. The function uses dscore::builtin_itembank by default.

Value

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

See also

Author

Stef van Buuren 2020

Examples

# difficulty levels in the GHAP lexicon get_tau(items = c("ddifmd001", "DDigmd052", "xyz"))
#> ddifmd001 DDigmd052 xyz #> 5.51 NA NA