getGroups.corStruct           package:nlme           R Documentation

Extract corStruct Groups

Description:

     This method function extracts the grouping factor associated with
     'object', if any is present.

Usage:

     ## S3 method for class 'corStruct':
     getGroups(object, form, level, data, sep)

Arguments:

  object: an object inheriting from class 'corStruct' representing a
          correlation structure.

    form: this argument is included to make the method function
          compatible with the generic. It will be assigned the value of
          'formula(object)' and should not be modified.

   level: this argument is included to make the method function
          compatible with the generic and is not used.

    data: an optional data frame in which to evaluate the variables
          defined in 'form', in case 'object' is not initialized and
          the grouping factor needs to be evaluated.

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

Value:

     if a grouping factor is present in the correlation structure
     represented by 'object', the function returns the corresponding
     factor vector; else the function returns 'NULL'.

Author(s):

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

See Also:

     'getGroups'

Examples:

     cs1 <- corAR1(form = ~ 1 | Subject)
     getGroups(cs1, data = Orthodont)

