Convert corStruct Object to Natural Parameterization
DESCRIPTION:
This method function converts
object to another
corStruct
object represented in a natural
parameterization. If
unconstrained is set to
TRUE, the
natural unconstrained parameterization used is the same as the one
used for
object, which is returned unchanged. The exceptions
are the
corSymm and
corBand classes (see the
documentation on the appropriate
asNatural method). If
unconstrained
is set to
FALSE, a constrained natural
parameterization is used to represent the object. In this case, a
constructor with the name
Nat appended to the end of the
original
object constructor is called (e.g.,
corAR1Nat
is called for
corAR1 objects).
corStruct objects with
constrained natural parameterization are represented by the
coefficients returned by
coef(object, uncons = FALSE), except
for
corSymm and
corBand objects (see the documentation
on
corSymmNat and
corBandNat, respectively).
USAGE:
asNatural(object, unconstrained)
REQUIRED ARGUMENTS:
object
an object inheriting from class
corStruct,
representing a correlation structure, whose
representation is to be converted to a natural parameterization.
OPTIONAL ARGUMENTS:
unconstrained
an optional logical value indicating whether the
natural parameterization should be unconstrained. Defaults to
TRUE.
VALUE:
If
unconstrained = TRUE,
object is returned unchanged
(except for
corSymm and
corBand objects), else, if
unconstrained = FALSE
, a
corStruct object
parameterized according to the constrained coefficients
corresponding to
object (except for
corSymm and
corBand
objects) - the class corresponding to these objects
is obtained by appending the name
Nat to the end of the
original class of
object.
SEE ALSO:
,
,
,
EXAMPLES:
cst1 <- corCompSymm(0.5, form = ~1|Subject)
cst1 <- initialize(cst1, data = Orthodont)
asNatural(cst1, unc = F)