#Set the working directory
getwd()
setwd("???")

require(OpenMx)
#Read in the data
data <-read.table("ozbmi2.txt", header=T, na.strings = "NA")
head(data)
# using subset function create new dataset without missing data
OZbmi <- subset(data, age !="NA" , select=c(bmi1, age)) 

RegModel <- mxModel("Regression",
    type="RAM", mxData(observed=OZbmi, type="raw"),
    manifestVars=c("age", "bmi1"), mxPath( from=c("age", "bmi1"), arrows=2, free=TRUE, values = c(1, 1), labels=c("varage", "residual")  ),  # variance paths
    mxPath( from="age", to="bmi1", arrows=1, free=TRUE, values=1, labels="beta1"),  # regression weights
    mxPath( from="one", to=c("age", "bmi1"), arrows=1, free=TRUE, values=c(21, .1), labels=c("meanage", "beta0") )# means and intercepts
) # close model
regFit <- mxRun(RegModel)
summary(regFit)