![Construct heterogeneous structured covariance matrices in SAS ARH(1) covariance structure](https://blogs.sas.com/content/iml/files/2022/12/covstructARH1.png)
A previous article describes how to use SAS IML software to construct common covariance structures that are encountered in mixed models. Each covariance matrix has several parameters, and you want to construct a matrix for any choice of the parameters. After you have constructed the covariance matrix, you can use