sim.data {ThurMod}

Create data based on Thurstonian model equations

Description

Simulates a data set of paired comparisons or ranking data based a Thurstonian latent utility model.

Usage

sim.data(nfactor = 1, nitem, nperson, itf, model = "factor",
  variables = NULL, ints = NULL, lmu = NULL, ivarcov = NULL,
  loadings = NULL, varcov = NULL, graded = FALSE, ncat = NULL,
  thres = NULL, transitive = TRUE, var = 0, fvalues = FALSE,
  sim = TRUE)

Arguments

nfactor

The number of factors. Defaults to 1.

nitem

The number of items.

nperson

The number of data points (= respondents) to simulate.

itf

A vector defining the items-to-factor relation. For example 'c(1,1,1,2,2,2)' defines six items, the first three correspond to factor 1, the second three correspond to factor 2.

model

The model class from which to simulate. Options are 'simple', 'factor', 'uc' and 'irt'. Defaults to 'factor'.

variables

A vector containing the names of paired comparison variables to return. If 'NULL' (default), all variables are returned.

ints

A vector defining the latent intercepts of item pairs.

lmu

A vector defining the latent means of items.

ivarcov

A matrix defining the variance-covariance matrix of the items.

loadings

A vector defining the loadings of items.

varcov

A matrix defining the variance-covariance matrix of the traits.

graded

Logical. Should a graded preference model be simulated? Defaults to 'FALSE'.

ncat

Numerical. The number of categories to specify for graded preference models. If graded = 'FALSE', ncat is 2.

thres

A vector of thresholds to categorize the latent difference response. If no thresholds are given, they are simulated from the distribution of the latent items. If graded = 'FALSE', the thresholds are all 0.

transitive

Logical. Should the data be transitive? If 'TRUE', ranking data is simulated, else paired comparison data is simulated. Defaults to 'TRUE'.

var

A vector containing the variances for each paired comparison. Defaults to 0.

fvalues

Logical. Should simulated factor values be returned? Defaults to 'FALSE'.

sim

Logical. Should the simulated data be returned? Defaults to 'TRUE'.

Details

The syntax currently is able to simulate data from the latent utility model (''simple'‘ and '’factor''; Maydeu-Olivares & Böckenholt, 2005) the unconstrained factor model (''uc''; Maydeu-Olivares & Böckenholt, 2005) and the IRT model(''irt''; Maydeu-Olivares & Brown, 2010).

Value

Returns a list containing the true factor scores and the data, or a matrix containing the data.

Examples

nfactor <- 3
nitem <- 15
nperson <- 1000
itf <- rep(1:3,5)
varcov <- diag(1,3)

# latent utility means
set.seed(69)
lmu <- runif(nitem, -1, 1)
loadings <- runif(nitem, 0.30, 0.95)

FC <- sim.data(nfactor=nfactor, nitem=nitem, nperson=nperson, itf=itf, 
varcov = varcov, lmu = lmu, loadings=loadings)