getGroups.corStruct function

Extract corStruct Groups

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

## 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 '/'.

Returns

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)

José Pinheiro and Douglas Bates bates@stat.wisc.edu

See Also

getGroups

Examples

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