R-DIF scaling functions for item intercepts/thresholds and slopes.

Computes the a scaling function using the item thresholds (d) and slopes (a) in groups = {0, 1}. The options are:

• "a_fun1": computes a2/a1

• "a_fun2": computes log(a2/a1)

• "d_fun1": computes (d2 - d1)/a1 for each threshold

• "d_fun2": computes (d2 - d1)/a2 for each threshold

• "d_fun3": computes (d2 - d1)/sqrt((a1^2 + a2^2)/2) for each threshold

Usage

y_fun(mle, fun = "d_fun3")

Arguments

mle

the output of get_model_parms

fun

one of c("a_fun1", "a_fun2", "d_fun1", "d_fun2", "d_fun3"). See description for details.

Value

A vector of scaling function values.

Details

Computes the scaling function specified by fun, for each item.