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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: Calculate Semi-variogram</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 Variogram.default {nlme}"><tr><td>Variogram.default {nlme}</td><td style="text-align: right;">R Documentation</td></tr></table> <h2>Calculate Semi-variogram</h2> <h3>Description</h3> <p>This method function calculates the semi-variogram for an arbitrary vector <code>object</code>, according to the distances in <code>distance</code>. For each pair of elements <i>x,y</i> in <code>object</code>, the corresponding semi-variogram is <i>(x-y)^2/2</i>. The semi-variogram is useful for identifying and modeling spatial correlation structures in observations with constant expectation and constant variance. </p> <h3>Usage</h3> <pre> ## Default S3 method: Variogram(object, distance, ...) </pre> <h3>Arguments</h3> <table summary="R argblock"> <tr valign="top"><td><code>object</code></td> <td> <p>a numeric vector with the values to be used for calculating the semi-variogram, usually a residual vector from a fitted model.</p> </td></tr> <tr valign="top"><td><code>distance</code></td> <td> <p>a numeric vector with the pairwise distances corresponding to the elements of <code>object</code>. The order of the elements in <code>distance</code> must correspond to the pairs <code>(1,2), (1,3), ..., (n-1,n)</code>, with <code>n</code> representing the length of <code>object</code>, and must have length <code>n(n-1)/2</code>.</p> </td></tr> <tr valign="top"><td><code>...</code></td> <td> <p>some methods for this generic require additional arguments. None are used in this method.</p> </td></tr> </table> <h3>Value</h3> <p>a data frame with columns <code>variog</code> and <code>dist</code> representing, respectively, the semi-variogram values and the corresponding distances. The returned value inherits from class <code>Variogram</code>. </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>Cressie, N.A.C. (1993), "Statistics for Spatial Data", J. Wiley & Sons. </p> <h3>See Also</h3> <p><code><a href="Variogram.html">Variogram</a></code>, <code><a href="Variogram.gls.html">Variogram.gls</a></code>, <code><a href="Variogram.lme.html">Variogram.lme</a></code>, <code><a href="plot.Variogram.html">plot.Variogram</a></code></p> <h3>Examples</h3> <pre> fm1 <- lm(follicles ~ sin(2 * pi * Time) + cos(2 * pi * Time), Ovary, subset = Mare == 1) Variogram(resid(fm1), dist(1:29))[1:10,] </pre> <hr /><div style="text-align: center;">[Package <em>nlme</em> version 3.1-139 <a href="00Index.html">Index</a>]</div> </body></html>