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 Bollen'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 ' fit <- sem(model, data=PoliticalDemocracy) summary(fit)
More information can be found on the website: http://lavaan.org