getGroups                package:nlme                R Documentation

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:

  object: any object

    form: an optional formula with a conditioning expression on its
          right hand side (i.e. an expression involving the '|'
          operator). Defaults to 'formula(object)'.

   level: a positive integer vector with the level(s) of grouping to be
          used when multiple nested levels of grouping are present.
          This argument is optional for most methods of this generic
          function and defaults to all levels of nesting.

    data: a data frame in which to interpret the variables named in
          'form'. Optional for most methods.

     sep: character, the separator to use between group levels when
          multiple levels are collapsed.  The default is ''/''.

Value:

     will depend on the method function used; see the appropriate
     documentation.

Author(s):

     Jose Pinheiro Jose.Pinheiro@pharma.novartis.com and Douglas Bates
     bates@stat.wisc.edu

References:

     Pinheiro, J.C., and Bates, D.M. (2000) "Mixed-Effects Models in S
     and S-PLUS", Springer, esp. pp. 100, 461.

See Also:

     'getGroupsFormula', 'getGroups.data.frame', 'getGroups.gls',
     'getGroups.lmList', 'getGroups.lme'

Examples:

     ## see the method function documentation

