modelscompete4 : An R Package for Comparing Nested and Non-nested Structural Equation Models

modelscompete4 is an R package for comparing nested and non-nested structural equation models (SEM). It streamlines the entire workflow by fitting a named list of model syntax strings, automatically detecting nesting relationships using parameter names and free-parameter counts, and applying the appropriate statistical test—likelihood ratio test for nested pairs and Vuong test for non-nested pairs. Unlike existing tools, it natively supports latent variables, handles any number of models simultaneously, and returns a comprehensive structured output including fit indices and a pairwise comparison matrix. Bootstrapped standard errors and parallel processing are also supported. The package is freely available on GitHub and CRAN.