Parameters | Predictive Modeling | Kernel Function

Corresponds to the same structure induced by random effects, which is the outer dot product of the Z matrix. This option is typically used when the covariance is approximately constant. Represent covariance structures in a class defined by Matérn^{1}. It is more general than the other structures and can include exponential or Gaussian functions.Note: The Matern kernel can take a long time to run due to its complex nature.

Note: For the spatial kernels you may need to add a PARMS statement in the PROC MIXED Additional Statements field to specify good starting values since the likelihood function can be multimodal. You also might need to relax the convergence tolerance, e.g. specify convg=1e-6 in the PROC MIXED Statement Options field. Refer to the REPEATED statement portion of the SAS PROC MIXED documentation for details