3 Further Operations and Applications

There exists a great variety of matrix operations and functions with much broader scope than the limited selection given in this chapter. For example, there are two other forms of matrix multiplication in common use, direct or kronecker products, and dot products. Similar extensions to addition and subtraction exist, and numerous matrix functions beyond determinant and trace can be defined. One place to study further operations is Searle (1982); applications and some definitions can be found in Neale (1997). We hope that the outline provided here will make understanding structural equation modeling of twin data much easier, and provide a starting point for those who wish to study the subject in more detail.