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