Simulate Data under a Parametric Logistic IRT Model
rpl simulates IRT data under a parametric logistic IRT model of type
"2PL", "3PL", "3PLu", "4PL", and "Rasch/1PL".
rpl(theta, a, b, g, u, return_setting = TRUE)
theta |
numeric vector of person parameters. Can also be a list, then a
list of length |
a |
numeric vector of item discrimination parameters. |
b |
numeric vector of item difficulty parameters. |
g |
numeric vector of so-called item guessing parameters. |
u |
numeric vector of item upper asymptote parameters. |
return_setting |
logical. Should a list containing slots of "a", "b", "g", "u", and "theta", as well as the simulated data matrix "data" be returned (default) or only the simulated data matrix. |
rpl returns either a list of the following components:
a |
numeric vector of item discrimination parameters used, |
b |
numeric vector of item difficulty parameters used, |
g |
numeric vector of item guessing parameters used, |
u |
numeric vector of item upper asymptote parameters used, |
theta |
numeric vector of person parameters used, |
data |
numeric matrix containing the simulated data, |
or (if return_setting = FALSE) only the numeric matrix containing the
simulated data.
set.seed(1) ## item responses under a 2PL (two-parameter logistic) model from ## 6 persons with three different person parameters ## 9 increasingly difficult items and corresponding discrimination parameters ## no guessing (= 0) and upper asymptote 1 ppar <- rep(c(-2, 0, 2), each = 2) ipar <- seq(-2, 2, by = 0.5) dpar <- rep(c(0.5, 1, 1.5), each = 3) sim <- rpl(theta = ppar, a = dpar, b = ipar, g = rep(0, 9), u = rep(1, 9)) ## simulated item response data along with setting parameters sim ## print and plot corresponding item response object iresp <- itemresp(sim$data) iresp plot(iresp)
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