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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: Overflow proof pdMat class for multiples of the identity...</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 pdIdnot {mgcv}"><tr><td>pdIdnot {mgcv}</td><td style="text-align: right;">R Documentation</td></tr></table> <h2>Overflow proof pdMat class for multiples of the identity matrix</h2> <h3>Description</h3> <p> This set of functions is a modification of the <code>pdMat</code> class <code>pdIdent</code> from library <code>nlme</code>. The modification is to replace the log parameterization used in <code>pdMat</code> with a <code><a href="notExp2.html">notLog2</a></code> parameterization, since the latter avoids indefiniteness in the likelihood and associated convergence problems: the parameters also relate to variances rather than standard deviations, for consistency with the <code><a href="pdTens.html">pdTens</a></code> class. The functions are particularly useful for working with Generalized Additive Mixed Models where variance parameters/smoothing parameters can be very large or very small, so that overflow or underflow can be a problem. </p> <p>These functions would not normally be called directly, although unlike the <code><a href="pdTens.html">pdTens</a></code> class it is easy to do so. </p> <h3>Usage</h3> <pre> pdIdnot(value = numeric(0), form = NULL, nam = NULL, data = sys.frame(sys.parent())) </pre> <h3>Arguments</h3> <table summary="R argblock"> <tr valign="top"><td><code>value</code></td> <td> <p>Initialization values for parameters. Not normally used.</p> </td></tr> <tr valign="top"><td><code>form</code></td> <td> <p>A one sided formula specifying the random effects structure. </p> </td></tr> <tr valign="top"><td><code>nam</code></td> <td> <p>a names argument, not normally used with this class.</p> </td></tr> <tr valign="top"><td><code>data</code></td> <td> <p>data frame in which to evaluate formula.</p> </td></tr> </table> <h3>Details</h3> <p>The following functions are provided: <code>Dim.pdIndot</code>, <code>coef.pdIdnot</code>, <code>corMatrix.pdIdnot</code>, <code>logDet.pdIdnot</code>, <code>pdConstruct.pdIdnot</code>, <code>pdFactor.pdIdnot</code>, <code>pdMatrix.pdIdnot</code>, <code>solve.pdIdnot</code>, <code>summary.pdIdnot</code>. (e.g. <code>mgcv:::coef.pdIdnot</code> to access.) </p> <p>Note that while the <code>pdFactor</code> and <code>pdMatrix</code> functions return the inverse of the scaled random effect covariance matrix or its factor, the <code>pdConstruct</code> function is initialised with estimates of the scaled covariance matrix itself. </p> <h3>Value</h3> <p> A class <code>pdIdnot</code> object, or related quantities. See the <code>nlme</code> documentation for further details.</p> <h3>Author(s)</h3> <p> Simon N. Wood <a href="mailto:simon.wood@r-project.org">simon.wood@r-project.org</a></p> <h3>References</h3> <p>Pinheiro J.C. and Bates, D.M. (2000) Mixed effects Models in S and S-PLUS. Springer </p> <p>The <code>nlme</code> source code. </p> <p><a href="http://www.maths.bris.ac.uk/~sw15190/">http://www.maths.bris.ac.uk/~sw15190/</a> </p> <h3>See Also</h3> <p><code><a href="te.html">te</a></code>, <code><a href="pdTens.html">pdTens</a></code>, <code><a href="notExp2.html">notLog2</a></code>, <code><a href="gamm.html">gamm</a></code></p> <h3>Examples</h3> <pre> # see gamm </pre> <hr /><div style="text-align: center;">[Package <em>mgcv</em> version 1.8-28 <a href="00Index.html">Index</a>]</div> </body></html>