SkewTk | R Documentation |
This function estimates the skewness of Cuzick and Edwards T_k test statistic under the RL hypothesis. Skewness of a random variable T is defined as E(T-μ)^3/(E(T-μ)^2)^{1.5} where μ=E T.
Skewness is used for Tango's correction to Cuzick and Edwards k
NN test statistic, T_k.
Tango's correction is a chi-square approximation, and its degrees of freedom is estimated using the skewness
estimate (see page 121 of \insertCitetango:2007;textualnnspat).
The argument, n_1, is the number of cases (denoted as n1
as an argument)
and k
is the number of NNs considered in T_k test statistic.
The argument of the function is the A_{ij} matrix, a
, which is the output of the function aij.mat
.
However, inside the function we symmetrize the matrix a
as b <- (a+a^t)/2
, to facilitate the formulation.
The number of cases are denoted as n_1 and number of controls as n_0 in this function to match the case-control class labeling, which is just the reverse of the labeling in \insertCitecuzick:1990;textualnnspat.
SkewTk(n1, k, a)
n1 |
Number of cases |
k |
Integer specifying the number of NNs (of subject i) |
a |
A_{ij} matrix which is the output of the function |
The skewness of Cuzick and Edwards T_k test statistic for disease clustering
Elvan Ceyhan
ceTk
, EV.Tk
, and varTk
n<-20 #or try sample(1:20,1) Y<-matrix(runif(3*n),ncol=3) cls<-sample(0:1,n,replace = TRUE) n1<-sum(cls==1) k<-sample(1:5,1) # try also 3, 5, sample(1:5,1) k a<-aij.mat(Y,k) SkewTk(n1,k,a)
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.