The grouping factors corresponding to the linear mixed-effects model
represented by object are extracted. If more than one level is
indicated in level, the corresponding grouping factors are
combined into a data frame; else the selected grouping factor is
returned as a vector.
Usage
getGroups(object, form, level)
Arguments
Value
either a data frame with columns given by the grouping factors
indicated in level, or, when a single level is requested, a
factor representing the selected grouping factor.