getGroups.gls {nlme} | R Documentation |
Extract gls Object Groups
Description
If present, the grouping factor associated to the correlation
structure for the linear model represented by object
is extracted.
Usage
## S3 method for class 'gls'
getGroups(object, form, level, data, sep)
Arguments
object |
an object inheriting from class |
form |
an optional formula with a conditioning expression on its
right hand side (i.e. an expression involving the |
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. Not used. |
data |
a data frame in which to interpret the variables named in
|
sep |
character, the separator to use between group levels when
multiple levels are collapsed. The default is |
Value
if the linear model represented by object
incorporates a
correlation structure and the corresponding corStruct
object
has a grouping factor, a vector with the group values is returned;
else, NULL
is returned.
Author(s)
José Pinheiro and Douglas Bates bates@stat.wisc.edu
See Also
Examples
fm1 <- gls(follicles ~ sin(2*pi*Time) + cos(2*pi*Time), Ovary,
correlation = corAR1(form = ~ 1 | Mare))
getGroups(fm1)