permutest.betadisper(vegan)
permutest.betadisper()所属R语言包：vegan
Permutation test of multivariate homogeneity of groups dispersions
多元同质化的群体分散体置换检验
译者：生物统计家园网 机器人LoveR
描述----------Description----------
Implements a permutation-based test of multivariate homogeneity of group dispersions (variances) for the results of a call to betadisper.
实现一个置换多元组分散均匀性（差异）为基础的测试的结果调用betadisper。
用法----------Usage----------
## S3 method for class 'betadisper'
permutest(x, pairwise = FALSE,
control = permControl(nperm = 999), ...)
参数----------Arguments----------
参数：x
an object of class "betadisper", the result of a call to betadisper.
类的一个对象"betadisper"，结果，调用betadisper。
参数：pairwise
logical; perform pairwise comparisons of group means?
逻辑执行组均值的两两比较的？
参数：control
a list of control values for the permutations to replace the default values returned by the function permControl
控制值的排列，以取代默认值返回一个列表的功能permControl
参数：...
Arguments passed to other methods.
参数传递给其他方法。
Details
详细信息----------Details----------
To test if one or more groups is more variable than the others, ANOVA of the distances to group centroids can be performed and parametric theory used to interpret the significance of F. An alternative is to use a permutation test. permutest.betadisper permutes model residuals to generate a permutation distribution of F under the Null hypothesis of no difference in dispersion between groups.
为了测试，如果一个或多个基团是比其他的更可变的，方差分析组矩心的距离可以执行和使用参数的理论来解释意义F.一种替代方法是使用一个置换试验。 permutest.betadisper置换，模型残差产生置换的F分布的零假设下不分散群体之间的差异。
Pairwise comparisons of group mean dispersions can be performed by setting argument pairwise to TRUE. A classical t test is performed on the pairwise group dispersions. This is combined with a permutation test based on the t statistic calculated on pairwise group dispersions. An alternative to the classical comparison of group dispersions, is to calculate Tukey's Honest Significant Differences between groups, via TukeyHSD.betadisper.
组两两比较，平均色散可以通过设置参数pairwiseTRUE。一个经典的t检验进行两两群分散体。这是结合与一个置换检验的t统计量计算成对组分散体的基础上。古典组比较分散体的另一种方法，是计算Tukey的诚实组间差异显着，通过TukeyHSD.betadisper。
值----------Value----------
permutest.betadisper returns a list of class "permutest.betadisper" with the following components:
permutest.betadisper返回一个列表类"permutest.betadisper"有以下组件：
参数：tab
the ANOVA table which is an object inheriting from class "data.frame".
方差分析表，它是一个对象，继承自类"data.frame"。
参数：pairwise
a list with components observed and permuted containing the observed and permuted p-values for pairwise comparisons of group mean distances (dispersions or variances).
组件的列表observed和permuted含有观察和置换p值两两比较，组平均距离（分散体或差异）。
参数：groups
character; the levels of the grouping factor.
字符;分组因子的水平的。
参数：control
a list, the result of a call to permControl.
一个列表，结果的呼叫permControl。
（作者）----------Author(s)----------
Gavin L. Simpson
参考文献----------References----------
multivariate dispersions. Biometrics <STRONG>62(1)</STRONG>, 245–253.
dispersion as a measure of beta diversity. Ecology Letters <STRONG>9(6)</STRONG>, 683–693.
参见----------See Also----------
For the main fitting function see betadisper. For an alternative approach to determining which groups are more variable,
的主要拟合函数betadisper。一种替代方法来确定哪些群体更多的变数，
实例----------Examples----------
data(varespec)
## Bray-Curtis distances between samples[＃布雷柯蒂斯样品之间的距离]
dis <- vegdist(varespec)
## First 16 sites grazed, remaining 8 sites ungrazed[＃前16的网站放牧，其余8个地点禁牧]
groups <- factor(c(rep(1,16), rep(2,8)), labels = c("grazed","ungrazed"))
## Calculate multivariate dispersions[＃计算多元分散体]
mod <- betadisper(dis, groups)
mod
## Perform test[＃进行测试]
anova(mod)
## Permutation test for F[＃置换检验为F]
permutest(mod, pairwise = TRUE)
## Tukey's Honest Significant Differences[＃Tukey的公正显着差异]
(mod.HSD <- TukeyHSD(mod))
plot(mod.HSD)
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。
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发表于 2012-10-1 15:11:08
