Question

我不是R.Anyway的高级用户我只想对两个数据集进行Wilcox测试：

library(coin)
GroupA = c(2,4,3,1,2,3,3,2,3,1)
GroupB = c(3,5,4,2,4,3,5,5,3,2)
g = factor(c(rep("GroupA", length(GroupA)), rep("GroupB", length(GroupB))))
v = c(GroupA, GroupB)
ss = wilcox_test(v ~ g, distribution="exact")

我想要的是获得Z值并计算效果大小。 ss是一个S4对象，当我打印它时，我看到它报告了一个Z值，但我在ss @statistic中找不到它。唯一具有我期望值的插槽是“测试统计”，但即使这是我测试时的测试的z值：

slot(ss, 'teststatistic')

我收到错误：

no slot of name "teststatistic" for this object of class "ScalarIndependenceTest"

任何人都可以给我一个提示吗？谢谢

Answer 1

S4类的print等效项是show方法，可以使用getMethod进行检查。在这种情况下，

ss
#
#   Exact Wilcoxon-Mann-Whitney Test
#
#data:  v by g (GroupA, GroupB)
#Z = -2.1095, p-value = 0.0385
#alternative hypothesis: true mu is not equal to 0

getMethod("show","ScalarIndependenceTest")
#Method Definition:
#
# function (object) 
# {
#     distname <- switch(class(object@distribution), AsymptNullDistribution = "Asymptotic", 
#         ApproxNullDistribution = "Approximative", ExactNullDistribution = "Exact")
#     RET <- list(statistic = setNames(object@statistic@teststatistic, 
#         nm = "Z"), p.value = object@distribution@pvalue(object@statistic@teststatistic), 
#         alternative = object@statistic@alternative, data.name = varnames(object@statistic), 
#         method = paste(distname, object@method))
#...
#...
# }

ss@statistic@teststatistic
#   GroupA 
#-2.109531 

ss@distribution@pvalue(ss@statistic@teststatistic)
#[1] 0.03850484

R：从S4对象获取槽的值（ScalarIndependenceTest）

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