# pdMat {nlme}

### Description

This function gives an alternative way of constructing an object inheriting from the `pdMat`

class named in `pdClass`

, or from `data.class(object)`

if `object`

inherits from `pdMat`

, and is mostly used internally in other functions. See the documentation on the principal constructor function, generally with the same name as the `pdMat`

class of object.

### Usage

pdMat(value, form, nam, data, pdClass)

### Arguments

- 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. 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. - pdClass
- an optional character string naming the
`pdMat`

class to be assigned to the returned object. This argument will only be used when`value`

is not a`pdMat`

object. Defaults to`"pdSymm"`

.

### Values

a `pdMat`

object representing a positive-definite matrix, inheriting from the class named in `pdClass`

, or from `class(object)`

, if `object`

inherits from `pdMat`

.

### References

Pinheiro, J.C., and Bates, D.M. (2000) "Mixed-Effects Models in S and S-PLUS", Springer.

### See Also

`pdClasses`

, `pdCompSymm`

, `pdDiag`

, `pdIdent`

, `pdNatural`

, `pdSymm`

, `reStruct`

, `solve.pdMat`

, `summary.pdMat`

Documentation reproduced from package nlme, version 3.1-127. License: GPL (>= 2)