OpenMx {OpenMx}R Documentation

OpenMx: An package for Structural Equation Modeling and Matrix Algebra Optimization

Description

OpenMx is a package for structural equation modeling, matrix algebra optimization and other statistical estimation problems. Try the example below. We try and have useful help files: for instance help(mxRun) to learn more. Also the reference manual

Details

OpenMx solves algebra optimization and statistical estimation problems using matrix algebra. Most users use it for Structural equation modeling.

The core function is mxModel, which makes a model. Models are containers for data, matrices, mxPaths algebras, bounds and constraints. Models most often have an expectation function (e.g., mxExpectationNormal) to calculate the expectations for the model. Models need a fit function. Several of these are built-in (e.g., mxFitFunctionML ) OpenMx also allows user-defined fit functions for purposes not covered by the built-in functions. (e.g., mxFitFunctionR or mxFitFunctionAlgebra).

Once built, the resulting mxModel can be run (i.e., optimized) using mxRun. This returns the fitted model.

You can see the resulting parameter estimates, algebra evaluation etc using summary(yourModel)

The user's manual is online (see reference below), but functions mxRun, mxModel, mxMatrix all have working examples to get you started as well.

The main OpenMx functions are: mxAlgebra, mxBounds, mxCI, mxConstraint, mxData, mxMatrix, mxModel, and mxPath

Expectation functions include mxExpectationNormal, mxExpectationRAM, mxExpectationLISREL, and mxExpectationStateSpace;

Fit functions include mxFitFunctionML, mxFitFunctionAlgebra, mxFitFunctionRow and mxFitFunctionR.

OpenMx comes with several useful datasets built-in. Access them using data(package="OpenMx")

To cite package 'OpenMx' in publications use:

Steven M. Boker, Michael C. Neale, Hermine H. Maes, Michael J. Wilde, Michael Spiegel, Timothy R. Brick, Jeffrey Spies, Ryne Estabrook, Sarah Kenny, Timothy C. Bates, Paras Mehta, and John Fox. (2011) OpenMx: An Open Source Extended Structural Equation Modeling Framework. Psychometrika.

Steven M. Boker, Michael C. Neale, Hermine H. Maes, Michael J. Wilde, Michael Spiegel, Timothy R. Brick, Ryne Estabrook, Timothy C. Bates, Paras Mehta, Timo von Oertzen, Ross J. Gore, Michael D. Hunter, Daniel C. Hackett, Julian Karch and Andreas M. Brandmaier. (2014) OpenMx 2 User Guide.

References

The OpenMx User's guide can be found at http://openmx.psyc.virginia.edu/documentation

Examples

library(OpenMx)
data(demoOneFactor)
# ===============================
# = Make and run a 1-factor CFA =
# ===============================

latents  = c("G") # the latent factor
manifests = names(demoOneFactor) # manifest variables to be modeled
# ====================
# = Make the MxModel =
# ====================
m1 <- mxModel("One Factor", type = "RAM",
	manifestVars = manifests, latentVars = latents,
	mxPath(from = latents, to = manifests),
	mxPath(from = manifests, arrows = 2),
	mxPath(from = latents, arrows = 2, free = FALSE, values = 1.0),
	mxData(cov(demoOneFactor), type = "cov", numObs = 500)
)

# ===============================
# = mxRun it and get a summary! =
# ===============================

m1 = mxRun(m1)
summary(m1, show = "std")

[Package OpenMx version 2.0.0-3948 Index]