psych (version 1.0-77)

sim: Functions to simulate psychological/psychometric data.

Description

A number of functions in the psych package will generate simulated data. These functions include link{sim} (for a factor simplex), and link{sim}( for a data simplex) sim.circ for a circumplex structure, sim.congeneric (for a one factor factor congeneric model), sim.dichot (to simulate dichotomous items), sim.hierarchical (a hierarchical factor model), sim.item (general item simulations), sim.structural (general simulation of structural models), sim.anova for ANOVA and lm simulatins, and sim.VSS. These functions are separately documented and are listed here for ease of the help function. See each function for more detailed help.

Usage

sim(fx=NULL,Phi=NULL,fy=NULL,n=0,mu=NULL,raw=FALSE)
sim.simplex(nvar =12, r=.8,mu=NULL, n=0)

Arguments

fx

The measurement model for x. If NULL, a 4 factor model is generated

Phi

The structure matrix of the latent variables

fy

The measurement model for y

mu

The means structure for the fx factors

n

Number of cases to simulate. If n=0 or NULL, the population matrix is returned.

raw

if raw=TRUE, raw data are returned as well.

nvar

Number of variables for a simplex structure

r

the base correlation for a simplex

Details

Simulation of data structures is a very useful tool in psychometric research and teaching. By knowing ``truth" it is possible to see how well various algorithms can capture it.

The default values for sim.structure is to generate a 4 factor, 12 variable data set with a simplex structure between the factors.

Other simulation functions in psych are:

sim.structure A function to combine a measurement and structural model into one data matrix. Useful for understanding structural equation models.

sim.congeneric A function to create congeneric items/tests for demonstrating classical test theory. This is just a special case of sim.structure. sim.hierarchical A function to create data with a hierarchical (bifactor) structure.

sim.item A function to create items that either have a simple structure or a circumplex structure.

sim.circ Create data with a circumplex structure.

sim.dichot Create dichotomous item data with a simple or circumplex structure.

sim.anova Simulate a 3 way balanced ANOVA or linear model, with or without repeated measures.

References

Revelle, W. (in preparation) An Introduction to Psychometric Theory with applications in R. Springer. at http://personality-project.org/r/book/

See Also

See above

Examples

simplex <- sim()
round(simplex$model,2)

congeneric <- sim.congeneric()
round(congeneric,2)
R <- sim.hierarchical()
R
fx <- matrix(c(.9,.8,.7,rep(0,6),c(.8,.7,.6)),ncol=2)
fy <- c(.6,.5,.4)
Phi <- matrix(c(1,0,.5,0,1,.4,0,0,0),ncol=3)
print(sim.structure(fx,Phi,fy,),digits=2)  
cor.plot(R) #show it graphically

simp <- sim.simplex()
#show the simplex structure using cor.plot
cor.plot(simp)