psych (version 1.0-25)

item.sim: Generate simulated data structures for circumplex or simple structure

Description

Rotations of factor analysis and principal components analysis solutions typically try to represent correlation matrices as simple structured. An alternative structure, appealing to some, is a circumplex structure where the variables are uniformly spaced on the perimeter of a circle in a two dimensional space. Generating these data is straightforward, and is useful for exploring alternative solutions to affect and personality structure.

Usage

item.sim(nvar = 72, nsub = 500, circum = FALSE, xloading = 0.6, yloading = 0.6, gloading = 0, xbias = 0, ybias = 0, categorical = FALSE, low = -3, high = 3, truncate = FALSE, cutpoint = 0)
circ.sim(nvar = 72, nsub = 500, circum = TRUE, xloading = 0.6, yloading = 0.6, gloading = 0, xbias = 0, ybias = 0, categorical = FALSE, low = -3, high = 3, truncate = FALSE, cutpoint = 0)

Arguments

nvar

Number of variables to simulate

nsub

Number of subjects to simulate

circum

circum=TRUE is circumplex structure, FALSE is simple structure

xloading

the average loading on the first dimension

yloading

Average loading on the second dimension

gloading

Average loading on a general factor (default=0)

xbias

To introduce skew, how far off center is the first dimension

ybias

To introduce skew on the second dimension

categorical

continuous or categorical variables.

low

values less than low are forced to low

high

values greater than high are forced to high

truncate

Change all values less than cutpoint to cutpoint.

cutpoint

What is the cutpoint

Value

• A data matrix of (nsub) subjects by (nvar) variables.

Details

This simulation was originally developed to compare the effect of skew on the measurement of affect (see Rafaeli and Revelle, 2005). It has been extended to allow for a general simulation of affect or personality items with either a simple structure or a circumplex structure. Items can be continuous normally distributed, or broken down into n categories (e.g, -2, -1, 0, 1, 2). Items can be distorted by limiting them to these ranges, even though the items have a mean of (e.g., 1).

References

Variations of a routine used in Rafaeli and Revelle, 2006; Rafaeli, E. & Revelle, W. (2006). A premature consensus: Are happiness and sadness truly opposite affects? Motivation and Emotion.

Acton, G. S. and Revelle, W. (2004) Evaluation of Ten Psychometric Criteria for Circumplex Structure. Methods of Psychological Research Online, Vol. 9, No. 1 http://www.dgps.de/fachgruppen/methoden/mpr-online/issue22/mpr110_10.pdf

See Also

See Also the implementation in this to generate numerous simulations. circ.simulation, circ.tests

Examples

round(cor(circ.sim(nvar=8,nsub=200)),2)
plot(factor.pa(circ.sim(16,500),2)$loadings) #circumplex structure
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plot(factor.pa(item.sim(16,500),2)$loadings) #simple structure
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