| pdCompSymm {nlme} | R Documentation |
This function is a constructor for the pdCompSymm class,
representing a positive-definite matrix with compound symmetry
structure (constant diagonal and constant off-diagonal elements). The
underlying matrix is represented by 2 unrestricted parameters.
When value is numeric(0), an unitialized pdMat
object, a one-sided formula, or a vector of character strings,
object is returned as an uninitialized pdCompSymm
object (with just some of its attributes and its class defined) and
needs to have its coefficients assigned later, generally using the
coef or matrix replacement functions. If value is
an initialized
pdMat object, object will be constructed from
as.matrix(value). Finally, if value is a numeric vector
of length 2, it is assumed to represent the unrestricted coefficients
of the underlying positive-definite matrix.
pdCompSymm(value, form, nam, data)
value |
an optional initialization value, which can be any of the
following: a pdMat object, a positive-definite
matrix, a one-sided linear formula (with variables separated by
+), a vector of character strings, or a numeric
vector of length 2. Defaults to numeric(0), corresponding to
an uninitialized object. |
form |
an optional one-sided linear formula specifying the
row/column names for the matrix represented by object. Because
factors may be present in form, the formula needs to be
evaluated on a data.frame to resolve the names it defines. This
argument is ignored when value is a one-sided
formula. Defaults to NULL. |
nam |
an optional vector of character strings specifying the
row/column names for the matrix represented by object. It must have
length equal to the dimension of the underlying positive-definite
matrix and unreplicated elements. This argument is ignored when
value is a vector of character strings. Defaults to
NULL. |
data |
an optional data frame in which to evaluate the variables
named in value and form. It is used to
obtain the levels for factors, which affect the
dimensions and the row/column names of the underlying matrix. If
NULL, no attempt is made to obtain information on
factors appearing in the formulas. Defaults to the
parent frame from which the function was called. |
a pdCompSymm object representing a positive-definite
matrix with compound symmetry structure, also inheriting from class
pdMat.
Jose Pinheiro Jose.Pinheiro@pharma.novartis.com and Douglas Bates bates@stat.wisc.edu
Pinheiro, J.C., and Bates, D.M. (2000) "Mixed-Effects Models in S and S-PLUS", Springer, esp. p. 161.
as.matrix.pdMat,
coef.pdMat,
matrix<-.pdMat,
pdClasses
pd1 <- pdCompSymm(diag(3) + 1, nam = c("A","B","C"))
pd1