pdMatrix {nlme} | R Documentation |

## Extract Matrix or Square-Root Factor from a pdMat Object

### Description

The positive-definite matrix represented by `object`

, or a
square-root factor of it is obtained. Letting *S* denote a
positive-definite matrix, a square-root factor of *S* is
any square matrix *L* such that *S =
L'L*. This function extracts *S* or *L*.

### Usage

pdMatrix(object, factor)

### Arguments

`object` |
an object inheriting from class `pdMat` , representing
a positive definite matrix. |

`factor` |
an optional logical value. If `TRUE` , a square-root
factor of the positive-definite matrix represented by `object`
is returned; else, if `FALSE` , the positive-definite matrix is
returned. Defaults to `FALSE` . |

### Value

if `fact`

is `FALSE`

the positive-definite matrix
represented by `object`

is returned; else a square-root of the
positive-definite matrix is returned.

### Author(s)

Jose Pinheiro Jose.Pinheiro@pharma.novartis.com and Douglas Bates bates@stat.wisc.edu

### See Also

`as.matrix.pdMat`

, `pdFactor`

,
`corMatrix`

### Examples

pd1 <- pdSymm(diag(1:4))
pdMatrix(pd1)

[Package

*nlme* version 3.1-66

Index]