rgpcm {psychotools}

Simulate Data under a Generalized Partial Credit Model

Description

rgpcm simulates IRT data under a generalized partial credit model.

Usage

rgpcm(theta, a, b, nullcats = FALSE, return_setting = TRUE)

Arguments

theta

numeric vector of person parameters. Can also be a list, then a list of length length(theta) is returned, containing multiple simulated data sets.

a

list of numerics of item discrimination parameters.

b

list of numeric vectors of item threshold parameters.

nullcats

logical. Should null categories be allowed?

return_setting

logical. Should a list containing slots of "a", "b", and "theta", as well as the simulated data matrix "data" be returned (default) or only the simulated data matrix?

Value

rgpcm returns either a list of the following components:

a

list of numerics of item discrimination parameters used,

b

list of numeric vectors of item threshold 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.

See Also

rpcm, rrsm, rpl, rrm

Examples

set.seed(1)
## item responses under a GPCM (generalized partial credit model) from
## 6 persons with three different person parameters
## 8 items with different combinations of two or three threshold parameters
## and corresponding discrimination parameters
ppar <- rep(-1:1, each = 2)
tpar <- rep(list(-2:0, -1:1, 0:1, 0:2), each = 2)
dpar <- rep(list(1, 2), each = 4)
sim <- rgpcm(theta = ppar, a = dpar, b = tpar)

## simulated item response data along with setting parameters
sim

## print and plot corresponding item response object
iresp <- itemresp(sim$data)
iresp
plot(iresp)