omega.graph {psych} R Documentation

Graph hierarchical factor structures

Description

Hierarchical factor structures represent the correlations between variables in terms of a smaller set of correlated factors which themselves can be represented by a higher order factor.

Two alternative solutions to such structures are found by the omega function. The correlated factors solutions represents the effect of the higher level, general factor, through its effect on the correlated factors. The other representation makes use of the Schmid Leiman transformation to find the direct effect of the general factor upon the original variables as well as the effect of orthogonal residual group factors upon the items.

Graphic presentations of these two alternatives are helpful in understanding the structure. omega.graph and omega.diagram draw both such structures. Graphs are drawn directly onto the graphics window or expressed in “dot" commands for conversion to graphics using implementations of Graphviz (if using omega.graph).

Using Graphviz allows the user to clean up the Rgraphviz output. However, if Graphviz and Rgraphviz are not available, use omega.diagram.

See the other structural diagramming functions, fa.diagram and structure.diagram.

Usage

omega.diagram(om.results,sl=TRUE,sort=TRUE,labels=NULL,cut=.2,gcut=.2,simple=TRUE,
errors=FALSE, digits=1,e.size=.1,rsize=.15,side=3,
main=NULL,cex=NULL,color.lines=TRUE,marg=c(.5,.5,1.5,.5), ...)
omega.graph(om.results, out.file = NULL,  sl = TRUE, labels = NULL, size = c(8, 6),
node.font = c("Helvetica", 14), edge.font = c("Helvetica", 10),
rank.direction=c("RL","TB","LR","BT"), digits = 1, title = "Omega", ...)

Arguments

 om.results The output from the omega function out.file Optional output file for off line analysis using Graphviz sl Orthogonal clusters using the Schmid-Leiman transform (sl=TRUE) or oblique clusters labels variable labels size size of graphics window node.font What font to use for the items edge.font What font to use for the edge labels rank.direction Defaults to left to right digits Precision of labels cex control font size color.lines Use black for positive, red for negative marg The margins for the figure are set to be wider than normal by default title Figure title main main figure caption ... Other options to pass into the graphics packages e.size the size to draw the ellipses for the factors. This is scaled by the number of variables. cut Minimum path coefficient to draw gcut Minimum general factor path to draw simple draw just one path per item sort sort the solution before making the diagram side on which side should errors be drawn? errors show the error estimates rsize size of the rectangles

Details

While omega.graph requires the Rgraphviz package, omega.diagram does not. codeomega requires the GPArotation package.

Value

 clust.graph A graph object sem A matrix suitable to be run throughe the sem function in the sem package.

Note

omega.graph requires rgraphviz. – omega requires GPArotation

Author(s)

http://personality-project.org/revelle.html
Maintainer: William Revelle revelle@northwestern.edu

References

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

Revelle, W. (1979). Hierarchical cluster analysis and the internal structure of tests. Multivariate Behavioral Research, 14, 57-74. (http://personality-project.org/revelle/publications/iclust.pdf)

Zinbarg, R.E., Revelle, W., Yovel, I., & Li. W. (2005). Cronbach's Alpha, Revelle's Beta, McDonald's Omega: Their relations with each and two alternative conceptualizations of reliability. Psychometrika. 70, 123-133. http://personality-project.org/revelle/publications/zinbarg.revelle.pmet.05.pdf

Zinbarg, R., Yovel, I., Revelle, W. & McDonald, R. (2006). Estimating generalizability to a universe of indicators that all have one attribute in common: A comparison of estimators for omega. Applied Psychological Measurement, 30, 121-144. DOI: 10.1177/0146621605278814 http://apm.sagepub.com/cgi/reprint/30/2/121

Examples

#24 mental tests from Holzinger-Swineford-Harman
if(require(GPArotation) ) {om24 <- omega(Harman74.cor\$cov,4) } #run omega

#
#example hierarchical structure from Jensen and Weng
if(require(GPArotation) ) {jen.omega <- omega(make.hierarchical())}

[Package psych version 1.4.5 Index]
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