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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><title>R: Extract Matrix or Square-Root Factor from a pdMat Object</title> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <link rel="stylesheet" type="text/css" href="R.css" /> </head><body> <table width="100%" summary="page for pdMatrix {nlme}"><tr><td>pdMatrix {nlme}</td><td style="text-align: right;">R Documentation</td></tr></table> <h2>Extract Matrix or Square-Root Factor from a pdMat Object</h2> <h3>Description</h3> <p>The positive-definite matrix represented by <code>object</code>, or a square-root factor of it is obtained. Letting <i>S</i> denote a positive-definite matrix, a square-root factor of <i>S</i> is any square matrix <i>L</i> such that <i>S = L'L</i>. This function extracts <i>S</i> or <i>L</i>. </p> <h3>Usage</h3> <pre> pdMatrix(object, factor) </pre> <h3>Arguments</h3> <table summary="R argblock"> <tr valign="top"><td><code>object</code></td> <td> <p>an object inheriting from class <code>pdMat</code>, representing a positive definite matrix.</p> </td></tr> <tr valign="top"><td><code>factor</code></td> <td> <p>an optional logical value. If <code>TRUE</code>, a square-root factor of the positive-definite matrix represented by <code>object</code> is returned; else, if <code>FALSE</code>, the positive-definite matrix is returned. Defaults to <code>FALSE</code>.</p> </td></tr> </table> <h3>Value</h3> <p>if <code>fact</code> is <code>FALSE</code> the positive-definite matrix represented by <code>object</code> is returned; else a square-root of the positive-definite matrix is returned. </p> <h3>Author(s)</h3> <p>José Pinheiro and Douglas Bates <a href="mailto:bates@stat.wisc.edu">bates@stat.wisc.edu</a></p> <h3>References</h3> <p>Pinheiro, J.C., and Bates, D.M. (2000) "Mixed-Effects Models in S and S-PLUS", Springer, esp. p. 162. </p> <h3>See Also</h3> <p><code><a href="as.matrix.pdMat.html">as.matrix.pdMat</a></code>, <code><a href="pdClasses.html">pdClasses</a></code>, <code><a href="pdFactor.html">pdFactor</a></code>, <code><a href="pdMat.html">pdMat</a></code>, <code><a href="pdMatrix.reStruct.html">pdMatrix.reStruct</a></code>, <code><a href="corMatrix.html">corMatrix</a></code> </p> <h3>Examples</h3> <pre> pd1 <- pdSymm(diag(1:4)) pdMatrix(pd1) </pre> <hr /><div style="text-align: center;">[Package <em>nlme</em> version 3.1-139 <a href="00Index.html">Index</a>]</div> </body></html>