nlme (version 3.1-86)

pdFactor: Square-Root Factor of a Positive-Definite Matrix

Description

A square-root factor of the positive-definite matrix represented by object is obtained. Letting $\Sigma$ denote a positive-definite matrix, a square-root factor of $\Sigma$ is any square matrix $L$ such that $\Sigma = L'L$. This function extracts $L$.

Usage

pdFactor(object)

Value

a vector with a square-root factor of the positive-definite matrix associated with object stacked column-wise.

References

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

See Also

pdMatrix

Examples

pd1 <- pdCompSymm(4 * diag(3) + 1)
pdFactor(pd1)