Description Value Note Author(s) References See Also

Standard classes of positive-definite matrices (`pdMat`

)
structures available in the `nlme`

package.

Available standard classes:

`pdSymm` |
general positive-definite matrix, with no additional structure |

`pdLogChol` |
general positive-definite matrix, with no additional structure, using a log-Cholesky parameterization |

`pdDiag` |
diagonal |

`pdIdent` |
multiple of an identity |

`pdCompSymm` |
compound symmetry structure (constant diagonal and constant off-diagonal elements) |

`pdBlocked` |
block-diagonal matrix, with diagonal blocks of any
"atomic" |

`pdNatural` |
general positive-definite matrix in natural parametrization (i.e. parametrized in terms of standard deviations and correlations). The underlying coefficients are not unrestricted, so this class should NOT be used for optimization. |

Users may define their own `pdMat`

classes by specifying a
`constructor`

function and, at a minimum, methods for the
functions `pdConstruct`

, `pdMatrix`

and `coef`

. For
examples of these functions, see the methods for classes `pdSymm`

and `pdDiag`

.

José Pinheiro and Douglas Bates [email protected]

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

`pdBlocked`

,
`pdCompSymm`

,
`pdDiag`

,
`pdFactor`

,
`pdIdent`

,
`pdMat`

,
`pdMatrix`

,
`pdNatural`

,
`pdSymm`

,
`pdLogChol`

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