formula.pdMat {nlme} | R Documentation |

## Extract pdMat Formula

### Description

This method function extracts the formula associated with a
`pdMat`

object, in which the column and row names are specified.

### Usage

## S3 method for class 'pdMat':
formula(x, asList, ...)

### Arguments

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

`asList` |
logical. Should the asList argument be applied to each
of the components? Never used. |

`...` |
some methods for this generic require additional
arguments. None are used in this method. |

### Value

if `x`

has a `formula`

attribute, its value is
returned, else `NULL`

is returned.

### Note

Because factors may be present in `formula(x)`

, the
`pdMat`

object needs to have access to a data frame where the
variables named in the formula can be evaluated, before it can resolve
its row and column names from the formula.

### Author(s)

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

### See Also

`pdMat`

### Examples

pd1 <- pdSymm(~Sex*age)
formula(pd1)

[Package

*nlme* version 3.1-66

Index]