Within-Group Variance

The variance functions are used to model heteroscedasticity in the within-group error.

Type The type of within-group variance function. The available functions are:

See the online Help for the corresponding varFunc S-PLUS function to determine the specific parameters for each of the variance functions.

Covariate Choose the variance covariate from the dropdown list.

Group Variables Choose the grouping factor(s) from the dropdown list. Multiple grouping factors are converted to ordered factors.

Parameters Enter parameters as needed for the different variance functions.