[.pdMat {nlme} | R Documentation |

## Subscript a pdMat Object

### Description

This method function extracts sub-matrices from the positive-definite
matrix represented by `x`

.

### Usage

x[i, j, drop]
x[i, j] <- value

### Arguments

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

`i, j` |
optional subscripts applying respectively to the rows
and columns of the positive-definite matrix represented by
`object` . When `i` (`j` ) is omitted, all rows (columns)
are extracted. |

`drop` |
a logical value. If `TRUE` , single rows or columns are
converted to vectors. If `FALSE` the returned value retains its
matrix representation. |

`value` |
a vector, or matrix, with the replacement values for the
relevant piece of the matrix represented by `x` . |

### Value

if `i`

and `j`

are identical, the returned value will be
`pdMat`

object with the same class as `x`

. Otherwise, the
returned value will be a matrix. In the case a single row (or column)
is selected, the returned value may be converted to a vector,
according to the rules above.

### Author(s)

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

### See Also

`[`

, `pdMat`

### Examples

pd1 <- pdSymm(diag(3))
pd1[1, , drop = FALSE]
pd1[1:2, 1:2] <- 3 * diag(2)

[Package

*nlme* version 3.1-57

Index]