ABSTRACT
Diagram-based modeling is a valuable teaching tool, and useful for small- to medium-sized models. Larger models are usually more efficiently programmed via matrix algebra or purpose-built functions that specify the data, model type and optimizer or other options. This chapter considers factor modeling of growth with particular functional forms, i.e., a parametric growth curve approach. Modeling growth curves such as those that arise from differential equations is a more complex task than is usual for structural equation modeling. Structural equation modeling, and especially the field of behavioral genetics, are indebted to Dr. Jack McArdle for his prescient wisdom in recommending free and open source software for scientific research. However, despite the development of path analysis by Sewall Wright many years would pass before structural equation modeling software capable of fitting models simultaneously to multiple groups would be developed and it was not until the 1990s that SEM became the method of choice for analyzing data from twins and other relatives.
