lavaan is a free, open source R package for latent variable analysis. You can use lavaan to estimate a large variety of multivariate statistical models, including path analysis, confirmatory factor analysis, structural equation modeling and growth curve models.

The lavaan package is developed to provide useRs, researchers and teachers a free open-source, but commercial-quality package for latent variable modeling. The long-term goal of lavaan is to implement all the state-of-the-art capabilities that are currently available in commercial packages. However, lavaan is still under development, and much work still needs to be done.

To get a first impression of how lavaan works in practice, consider the following example of a SEM model (the Political Democracy Example from Bollenâ€™s 1989 book):

```
library(lavaan)
<- '
model # latent variable definitions
ind60 =~ x1 + x2 + x3
dem60 =~ y1 + y2 + y3 + y4
dem65 =~ y5 + y6 + y7 + y8
# regressions
dem60 ~ ind60
dem65 ~ ind60 + dem60
# residual covariances
y1 ~~ y5
y2 ~~ y4 + y6
y3 ~~ y7
y4 ~~ y8
y6 ~~ y8
'
<- sem(model, data=PoliticalDemocracy)
fit summary(fit)
```

More information can be found on the website: http://lavaan.org