omogeneous variance)</p></li>
<li><p><code>cs</code> (compound symmetric, heterogeneous variance)</p></li>
<li><p><code>ou</code> (* Ornstein-Uhlenbeck, homogeneous variance)</p></li>
<li><p><code>exp</code> (* exponential autocorrelation)</p></li>
<li><p><code>gau</code> (* Gaussian autocorrelation)</p></li>
<li><p><code>mat</code> (* Matérn process correlation)</p></li>
<li><p><code>toep</code> (* Toeplitz)</p></li>
<li><p><code>rr</code> (reduced rank/factor-analytic model)</p></li>
<li><p><code>homdiag