covTcomb: Covariance matrix for T_k values in 'Tcomb'
In nnspat: Nearest Neighbor Methods for Spatial Patterns

covTcomb

R Documentation

Covariance matrix for `T_k` values in `Tcomb`

Description

This function computes the covariance matrix for the T_k values used in the T_{comb} test statistics, which is a linear combination of some T_k tests.

The argument, n_1, is the number of cases (denoted as n1 as an argument). The number of cases is denoted as n_1 to match the case-control class labeling, which is just the reverse of the labeling in \insertCitecuzick:1990;textualnnspat.

The argument klist is the vector of integers specifying the indices of the T_k values used in obtaining the T_{comb}.

The logical argument nonzero.mat (default=TRUE) is for using the A matrix if FALSE or just the matrix of nonzero locations in the A matrix (if TRUE) in the computations.

The logical argument asy.cov (default=FALSE) is for using the asymptotic covariance or the exact (i.e., finite sample) covariance for the vector of T_k values used in Tcomb. If asy.cov=TRUE, the asymptotic covariance is used, otherwise the exact covariance is used.

See page 87 of (\insertCitecuzick:1990;textualnnspat) for more details.

Usage

covTcomb(dat, n1, klist, nonzero.mat = TRUE, asy.cov = FALSE, ...)

Arguments

`dat`	The data set in one or higher dimensions, each row corresponds to a data point.
`n1`	Number of cases
`klist`	`list` of integers specifying the indices of the `T_k` values used in obtaining the `T_{comb}`.
`nonzero.mat`	A logical argument (default is `TRUE`) to determine whether the `A` matrix or the matrix of nonzero locations of the `A` matrix will be used in the computation of `N_s` and `N_t`. If `TRUE` the nonzero location matrix is used, otherwise the `A` matrix itself is used.
`asy.cov`	A logical argument (default is `FALSE`) to determine whether asymptotic or exact (i.e., finite sample) covariances between `T_k` and `T_l` values are to be used to obtain the entries of the covariance matrix. If `TRUE` the asymptotic covariance values are used, otherwise exact covariance values are used.
`...`	are for further arguments, such as `method` and `p`, passed to the `dist` function.

Value

Returns the covariance matrix for the T_k values used in Tcomb.

Author(s)

Elvan Ceyhan

References

\insertAllCited

Examples

n<-20  #or try sample(1:20,1)
Y<-matrix(runif(3*n),ncol=3)
cls<-sample(0:1,n,replace = TRUE)  #or try cls<-rep(0:1,c(10,10))
n1<-sum(cls==1)

kl<-sample(1:5,3) #try also sample(1:5,2)
kl
covTcomb(Y,n1,kl)
covTcomb(Y,n1,kl,method="max")
covTcomb(Y,n1,kl,nonzero.mat = FALSE)

covTcomb(Y,n1,kl,asy=TRUE)

nnspat documentation built on May 29, 2024, 10:03 a.m.