Posts by Pairach

sem package in R: a sample of transaction cost measurement

A sneak peek of the result of a Structural Equation Model using sem package in R.

I will present in the R User Conference in Warwick next week, is reveal first here.

The following are the codes of ‘sem’ package I used in the paper.

You may also view the code of other packages to run SEM models as well.

• Codes for lavaan package
• Code for OpenMx package
• Other packages for SEM analysis

##-------------------------------------------------##
##    Measuring Transaction Cost in Supply Chains  ##
##               Pairach Piboonrungroj             ##
##         R useR conference August 2011           ##
##-------------------------------------------------##
install.packages("sem")
library(sem)

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

#Input covariance matrix
data.tc.1 <- cor(hoteldata)

# Have a look at the top of the data
# to check it we import the right one
head(data.tc.1)

#Create an object contains correlation matrix of the data for fitting the model in the next step
hotel.cor <- cor(hoteldata)
#  path parameter  start-value
model.TC.1 <- specify.model()
	TC   -> TC1,    gamma1,  NA # measurement item
	TC   -> TC2,    gamma2,  NA
 	TC   -> TC3,    gamma3,  NA
 	TC   -> TC6,    gamma6,  NA
 	TC   -> TC7,    gamma7,  NA
 	TC   -> TC11,   gamma11, NA
 	TC   -> TC13,   gamma13, NA
 	TC1  <-> TC1,	e1,      NA # measurement error
 	TC2  <-> TC2,	e2,      NA
 	TC3  <-> TC3,	e3,      NA
 	TC6  <-> TC6,	e6,      NA
 	TC7  <-> TC7,	e7,      NA
 	TC11 <-> TC11,	e11,     NA
 	TC13 <-> TC13,	e13,     NA
 	TC   <-> TC,    NA,      1

model.TC.1

sem.TC.1 <- sem(model.TC.1, data.tc.1, 53)
# print result (fit indices, parameters, hypothesis tests)
summary(sem.TC.1)
# standardised coefficients (loadings)
std.coef(sem.TC.1)