How to Fit a Structural Equation Model in Displayr – Displayr Help

In this article, we will walk through the steps of fitting a structural equation model (SEM) in Displayr. The post assumes you already know what an SEM is and how to interpret it.

Case study

I am going to analyze Bollen's famous Political Democracy data set (Kenneth Bollen (1989), Structural Equations with Latent Variables, Wiley.)

Requirements

A Displayr Document with data suitable for structural equation modeling.

Method

Step 1: Load the data

Typically, data sets are loaded into Displayr from raw data files. In this case, we will load data from an R package.

Go to Data Sources > Plus (+) > R.
Under Name, enter the name BollenPoliticalDemocracy for the data set.
Paste the code below into the Code panel and click OK.
```
library(sem)
Bollen
```

Step 2: Fit the model

The difficult step is fitting the model, which requires specifying the measurement model, the relationships to be tested (i.e., the regressions), and the model's correlation structure. For more information, please check out the lavaan website.

To do this:

From the toolbar or from + in the Report tree, select Calculation > Custom Code.

Paste the code below into the Code panel and click Calculate.

# Load the package for computing the SEM
library(lavaan)

# Describe the model
model <- '
    #measurement model
        ind60 =~ x1 + x2 + x3
        dem60 =~ y1 + y2 + y3 + y4
        dem65 =~ y5 + y6 + y7 + y8
    #regressions
        dem60 ~ ind60
        dem65 ~ ind60 + dem60
    #residual corrections
        y1 ~~ y5
        y2 ~~ y4 + y6
        y3 ~~ y7
        y4 ~~ y8
        y6 ~~ y8'

# Assemble the raw data into a data frame, using the variable names
# from the raw data
df = data.frame(y1, y2, y3, y4, y5, y6, y7, y8, x1, x2, x3)

# Fit the model
fit <- sem(model, data = df)

The output will appear as:

Step 3: Review the path diagram

To check that the model has been correctly specified, it's a good idea to review the path diagram.

From the toolbar or from the + menu in the Report tree, select Calculation > Custom Code.
Paste in the code below and click Calculate.
```
library(semPlot)
semPaths(fit)
```

The output will appear as:

Step 4: Extract the summary statistics

From the toolbar or from the + menu in the Report tree, select Calculation > Custom Code.
Paste in the code below into the Code panel and click Calculate.
```
summary(fit)
```
To align the text neatly, go to Properties > Appearance > Appearance > Font and set the font to Courier New.