OpenMx package for Structural Equation Model in R

OpenMx (Boker et al, 2011) is claimed to be a “ free and open source software for use with R that allows estimation of a wide variety of advanced multivariate statistical models.” contributed by experts in R and SEM.

The following is my OpenMx script I used in my presentation at R useR! 2011.

##-------------------------------------------------##
##    Measuring Transaction Cost in Supply Chains  ##
##               Pairach Piboonrungroj             ##
##         R useR conference August 2011           ##
##-------------------------------------------------##

#install OpenMx
source('http://openmx.psyc.virginia.edu/getOpenMx.R')
require(OpenMx)

# load the OpenMx package into R

library(OpenMx)

# read the data into an R dataframe

hoteldata <- read.csv("http://dl.dropbox.com/u/46344142/useR2011/cleandata.csv")

# define which indicators load on each factor

indicatorsTC <- c("TC1", "TC2", "TC3", "TC6", "TC7" , "TC11" , "TC13")

indicatorsAS <- c("AS1", "AS2")

indicatorsUN <- c("UN1", "UN2")

# create a vector of all of the manifest variables

manifests <- c(indicatorsTC, indicatorsAS, indicatorsUN)

# define which indicator is to be used to scale each factor

scaleTC <- c("TC1")

scaleAS <- c("AS1")

scaleUN <- c("UN1")

# define the names of the factors

latents <- c("TC", "AS", "UN")

# define the MxModel and store it into "factorModel"

factorModel <- mxModel("TC Model",

type="RAM",

manifestVars = manifests,

latentVars = latents,

# specify the free factor loadings

mxPath(from="TC", to=indicatorsTC, free=TRUE, values=.2),

mxPath(from="AS", to=indicatorsAS, free=TRUE, values=.2),

mxPath(from="UN", to=indicatorsUN, free=TRUE, values=.2),

# scale the two latent variables

mxPath(from="TC", to=scaleTC, free=FALSE, values=1),

mxPath(from="AS", to=scaleAS, free=FALSE, values=1),

mxPath(from="UN", to=scaleUN, free=FALSE, values=1),

# specify the unique variances

mxPath(from=manifests, arrows=2, free=TRUE, values=.8),

# specify the factor variances

mxPath(from=latents, arrows=2, free=TRUE, values=.8),

# specify the path

mxPath(from="AS", to="TC", arrows=2, free=TRUE, values=.3),

mxPath(from="UN", to="TC", arrows=2, free=TRUE, values=.3),

mxPath(from="AS", to="UN", arrows=2, free=TRUE, values=.3),

# specify the mean structure

mxPath(from="one", to=c(manifests, latents), arrows=1, free=FALSE, values=0),

# attach the data to the model

mxData(hoteldata, type="raw")

)

# run the factor model

factorModelOut <- mxRun(factorModel)

# print a summary of the results

summary(factorModelOut)
<pre>

See more details about the model and the comparison with other R packages and software