getGroups: Extract Grouping Factors from an Object
Description
This function is generic; method functions can be written to handle
specific classes of objects. Classes which already have methods for
this function include corStruct, data.frame,
gls, lme, lmList, and varFunc.
Usage
getGroups(object, form, level, data, sep)
Arguments
Value
will depend on the method function used; see the appropriate documentation.
References
Pinheiro, J.C., and Bates, D.M. (2000) "Mixed-Effects Models
in S and S-PLUS", Springer, esp. pp. 100, 461.