Structural Equation Modeling With Ωnyx

Abstract

Ωnyx is a free software environment for creating and estimating structural equation models (SEM). It provides a graphical user interface that facilitates an intuitive creation of models, and a powerful back end for performing maximum likelihood estimation of parameters. Path diagrams in Ωnyx can be exported to OpenMx, lavaan, and Mplus to allow an easy transition to script-based SEM software. Also, OpenMx scripts can be transformed into a path diagrams in Ωnyx. In addition to the graphical user interface, Ωnyx provides a maximum likelihood optimizer that finds multiple minima and does not require the user to provide starting values. To our knowledge, Ωnyx is the only SEM program that provides multiple optima. This article describes both the graphical and conceptual features of Ωnyx, including the optimization approach, and demonstrates two hands-on modeling examples.