localG(spdep)
localG()所属R语言包：spdep
G and Gstar local spatial statistics
G和的GSTAR本地空间统计
译者：生物统计家园网 机器人LoveR
描述----------Description----------
The local spatial statistic G is calculated for each zone based on the spatial weights object used. The value returned is a Z-value, and may be used as a diagnostic tool. High positive values indicate the posibility of a local cluster of high values of the variable being analysed, very low relative values a similar cluster of low values. For inference, a Bonferroni-type test is suggested in the references, where tables of critical values may be found (see also details below).
局部空间统计G被反对使用的空间权重的基础上为每个区域计算。返回的值是一个Z值，并可以被用作一种诊断工具。高的正值表示被分析的变量，一个类似的聚类的非常低的相对值低的值的高值的本地聚类posibility。进行推理，邦费罗尼类型的测试，建议在参考文献中，在那里可能会发现表中的临界值（见下面还详细介绍）。
用法----------Usage----------
localG(x, listw, zero.policy=NULL, spChk=NULL)
参数----------Arguments----------
参数：x
a numeric vector the same length as the neighbours list in listw
一个数值向量相同的长度的邻居列表中listw
参数：listw
a listw object created for example by nb2listw
例如创建一个listw对象的nb2listw
参数：zero.policy
default NULL, use global option value; if TRUE assign zero to the lagged value of zones without neighbours, if FALSE assign NA
默认为空，请使用全局选项的值，如果真没有邻居的滞后值的区域分配了零，如果为FALSE分配NA
参数：spChk
should the data vector names be checked against the spatial objects for identity integrity, TRUE, or FALSE, default NULL to use get.spChkOption()
应的数据向量空间对象的名称进行核对身份完整性，TRUE，否则返回FALSE，默认为空，使用get.spChkOption()
Details
详细信息----------Details----------
If the neighbours member of listw has a "self.included" attribute set to TRUE, the Gstar variant, including the self-weight w_{ii} > 0, is calculated and returned. The returned vector will have a "gstari" attribute set to TRUE. Self-weights can be included by using the include.self function in the spweights package before converting the neighbour list to a spatial weights list with nb2listw as shown below in the example.
如果的邻居成员listw的有一个“self.included”的属性设置为TRUE，GSTAR的变体，包括自重w_{ii} > 0，计算并返回。返回的向量将有一个“gstari”属性设置为TRUE。自权重可以使用include.self功能在spweights包，然后将其转换邻居列表空间权重列表nb2listw如下图所示的例子。
The critical values of the statistic under assumptions given in the references for the 95th percentile are for n=1: 1.645, n=50: 3.083, n=100: 3.289, n=1000: 3.886.
在参考文献中的第95个百分位数的假设条件下的临界值的统计为n = 1：1.645，N = 50：3.083，N = 100：3.289，N = 1000：3.886。
值----------Value----------
A vector of G or Gstar values, with attributes "gstari" set to TRUE or FALSE, "call" set to the function call, and class "localG".
一个矢量的G或GSTAR值，带有属性“gstari”设置为TRUE或FALSE，“呼”的函数调用，类的“localG”。
（作者）----------Author(s)----------
Roger Bivand <a href="mailto:Roger.Bivand@nhh.no">Roger.Bivand@nhh.no</a>
参考文献----------References----------
statistics: distributional issues and an application. Geographical Analysis, 27, 286–306; Getis, A. and Ord, J. K. 1996 Local spatial statistics: an overview. In P. Longley and M. Batty (eds) Spatial analysis: modelling in a GIS environment (Cambridge: Geoinformation
实例----------Examples----------
data(getisord)
xycoords <- cbind(xyz$x, xyz$y)
nb30 <- dnearneigh(xycoords, 0, 30)
G30 <- localG(xyz$val, nb2listw(nb30, style="B"))
G30[length(xyz$val)-136]
nb60 <- dnearneigh(xycoords, 0, 60)
G60 <- localG(xyz$val, nb2listw(nb60, style="B"))
G60[length(xyz$val)-136]
nb90 <- dnearneigh(xycoords, 0, 90)
G90 <- localG(xyz$val, nb2listw(nb90, style="B"))
G90[length(xyz$val)-136]
nb120 <- dnearneigh(xycoords, 0, 120)
G120 <- localG(xyz$val, nb2listw(nb120, style="B"))
G120[length(xyz$val)-136]
nb150 <- dnearneigh(xycoords, 0, 150)
G150 <- localG(xyz$val, nb2listw(nb150, style="B"))
G150[length(xyz$val)-136]
brks <- seq(-5,5,1)
cm.col <- cm.colors(length(brks)-1)
image(x, y, t(matrix(G30, nrow=16, ncol=16, byrow=TRUE)),
breaks=brks, col=cm.col, asp=1)
text(xyz$x, xyz$y, round(G30, digits=1), cex=0.7)
polygon(c(195,225,225,195), c(195,195,225,225), lwd=2)
title(main=expression(paste("Values of the ", G[i], " statistic")))
G30s <- localG(xyz$val, nb2listw(include.self(nb30),
style="B"))
cat("value according to Getis and Ord's eq. 14.2, p. 263 (1996)\n")
G30s[length(xyz$val)-136]
cat(paste("value given by Getis and Ord (1996), p. 267",
"(division by n-1 rather than n \n in variance)\n"))
G30s[length(xyz$val)-136] *
(sqrt(sum(scale(xyz$val, scale=FALSE)^2)/length(xyz$val)) /
sqrt(var(xyz$val)))
image(x, y, t(matrix(G30s, nrow=16, ncol=16, byrow=TRUE)),
breaks=brks, col=cm.col, asp=1)
text(xyz$x, xyz$y, round(G30s, digits=1), cex=0.7)
polygon(c(195,225,225,195), c(195,195,225,225), lwd=2)
title(main=expression(paste("Values of the ", G[i]^"*", " statistic")))
转载请注明:出自 生物统计家园网(http://www.biostatistic.net)。
注：
注1：为了方便大家学习，本文档为生物统计家园网机器人LoveR翻译而成，仅供个人R语言学习参考使用，生物统计家园保留版权。
注2：由于是机器人自动翻译，难免有不准确之处，使用时仔细对照中、英文内容进行反复理解，可以帮助R语言的学习。
注3：如遇到不准确之处，请在本贴的后面进行回帖，我们会逐渐进行修订。
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发表于 2012-9-30 14:40:35
