.\" -*- nroff -*- generated from .Rd format
.BG
.FN corStrat
.TL
Stratified Correlation Structure
.DN
This function is a constructor for the `corStrat' class,
representing a set of correlation structures corresponding to
different strata, defined by `strata'. Different `corStruct'
classes can be used for different strata.  The number
of coefficients associated with this class is equal to the sum of the
number of coefficients of each `corStruct' object it includes.
Objects created using this constructor must later be initialized
using the appropriate `initialize' method.
.CS
corStrat(value, form, strata)
.RA
.AG value
a `corStruct' object, or a list of `corStruct'
objects. If given as a single object, it is repeated for all strata.
.AG strata
a one-sided formula specifying the stratification variable
for the different `corStruct' objects represented by
`object'. Its right hand side must evaluate to a factor or an
integer.
.OA
.AG form
an optional one sided formula of the form `~ t', or
`~ t | g', specifying a time covariate `t' and,  optionally, a
grouping factor `g'. The same formula is used for all
corStruct represented in `object'. When a grouping factor is
present, the correlation structure is assumed to apply only 
to observations within the same grouping level; observations with
different grouping levels are assumed to be uncorrelated.
.RT
a `corStrat' object representing a set of correlation structures
corresponding to different strata.

.SA
`initialize.corStruct'
.EX
cs1 <- corStrat(corAR1(0.2, form = ~ 1 | Subject), strata = ~ Sex)
cs1 <- corStrat(list(Male = corAR1(), Female = corARMA(p=2)),
                form = ~ 1 | Subject, strata = ~ Sex)
.KW models
.WR
