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)



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.


A string that selects a subset in the itembank that makes up the key, the set of difficulty estimates from a fitted Rasch model. The built-in keys are: "gsed2212" (default), "gsed2208" (deprecated), "gsed2206" (deprecated), "gsed1912", "lf2206", "sf2206", "gcdg", and "dutch". Since version 1.5.0, the key = "gsed" selects the latest key starting with the string "gsed". Use key = "" to use all item names, which should only be done if there are no duplicate itemnames in the 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.


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


Stef van Buuren 2020


# difficulty levels in the GHAP lexicon
get_tau(items = c("ddifmd001", "DDigmd052", "xyz"))
#> ddifmd001 DDigmd052       xyz 
#>      8.61        NA        NA