funsZnnsym.ss: Pielou's Pairwise NN Symmetry Test with Normal Approximation (for Sparse Sampling)

Description

Two functions: Znnsym.ss.ct and Znnsym.ss.

Both functions are objects of class "cellhtest" but with different arguments (see the parameter list below). Each one performs hypothesis tests of equality of the expected values of the off-diagonal cell counts (i.e., entries) for each pair \(i,j\) of classes under RL or CSR in the NNCT for \(k \ge 2\) classes. That is, each performs Pielou's first type of NN symmetry test which is appropriate (i.e., have the appropriate asymptotic sampling distribution) provided that data is obtained by sparse sampling. (See ceyhan:SWJ-spat-sym2014;textualnnspat for more detail).

Each symmetry test is based on the normal approximation of the differences of the off-diagonal entries in the NNCT and are due to pielou:1961;textualnnspat.

Each function yields a contingency table of the test statistics, \(p\)-values for the corresponding alternative, expected values, lower and upper confidence levels, sample estimates (i.e., observed values) and null value(s) (i.e., expected values) for the \(N_{ij}-N_{ji}\) values for \(i \ne j\) (all in the upper-triangular form except for the null value, which is 0 for all pairs) and also names of the test statistics, estimates, null values, the description of the test, and the data set used.

The null hypothesis is that all \(E(N_{ij})=E(N_{ji})\) for \(i \ne j\) in the \(k \times k\) NNCT (i.e., symmetry in the mixed NN structure) for \(k \ge 2\). In the output, the test statistic, \(p\)-value and the lower and upper confidence limits are valid only for (properly) sparsely sampled data.

See also (pielou:1961,ceyhan:SWJ-spat-sym2014;textualnnspat) and the references therein.

Usage

Znnsym.ss.ct(
  ct,
  alternative = c("two.sided", "less", "greater"),
  conf.level = 0.95
)
Znnsym.ss(
  dat,
  lab,
  alternative = c("two.sided", "less", "greater"),
  conf.level = 0.95,
  ...
)

Value

A list with the elements

statistic: The matrix of \(Z\) test statistics for Pielou's first type of NN symmetry test (in the upper-triangular form)
stat.names: Name of the test statistics
p.value: The matrix of \(p\)-values for the hypothesis test for the corresponding alternative (in the upper-triangular form)
LCL,UCL: Matrix of Lower and Upper Confidence Levels (in the upper-triangular form) for the \(N_{ij}-N_{ji}\) values for \(i \ne j\) at the given confidence level conf.level and depends on the type of alternative.
conf.int: The confidence interval for the estimates, it is NULL here, since we provide the UCL and LCL in matrix form.
cnf.lvl: Level of the upper and lower confidence limits (i.e., conf.level) of the differences of the off-diagonal entries.
estimate: Estimates of the parameters, i.e., matrix of the difference of the off-diagonal entries (in the upper-triangular form) of the \(k \times k\) NNCT, \(N_{ij}-N_{ji}\) for \(i \ne j\).
est.name,est.name2: Names of the estimates, former is a shorter description of the estimates than the latter.
null.value: Hypothesized null value for the expected difference between the off-diagonal entries, \(E(N_{ij})-E(N_{ji})\) for \(i \ne j\) in the \(k \times k\) NNCT, which is 0 for this function.
null.name: Name of the null values
alternative: Type of the alternative hypothesis in the test, one of "two.sided", "less", "greater"
method: Description of the hypothesis test
ct.name: Name of the contingency table, ct, returned by Znnsym.ss.ct only
data.name: Name of the data set, dat, returned by Znnsym.ss only

Arguments

ct: A nearest neighbor contingency table, used in Znnsym.ss.ct only
alternative: Type of the alternative hypothesis in the test, one of "two.sided", "less" or "greater".
conf.level: Level of the upper and lower confidence limits, default is 0.95, for the difference of the off-diagonal entries, \(N_{ij}-N_{ji}\)
dat: The data set in one or higher dimensions, each row corresponds to a data point, used in Znnsym.ss only
lab: The vector of class labels (numerical or categorical), used in Znnsym.ss only
...: are for further arguments, such as method and p, passed to the dist function. used in Znnsym.ss only

Author

Elvan Ceyhan

References

Examples

Run this code

n<-20  #or try sample(1:20,1)
Y<-matrix(runif(3*n),ncol=3)
ipd<-ipd.mat(Y)
cls<-sample(1:2,n,replace = TRUE)  #or try cls<-rep(1:2,c(10,10))
ct<-nnct(ipd,cls)
ct

Znnsym.ss(Y,cls)
Znnsym.ss.ct(ct)

Znnsym.ss(Y,cls,method="max")

Znnsym.ss(Y,cls,alt="g")
Znnsym.ss.ct(ct,alt="g")

#cls as a factor
na<-floor(n/2); nb<-n-na
fcls<-rep(c("a","b"),c(na,nb))
Znnsym.ss(Y,fcls)

#############
n<-40
Y<-matrix(runif(3*n),ncol=3)
ipd<-ipd.mat(Y)
cls<-sample(1:4,n,replace = TRUE)  #or try cls<-rep(1:2,c(10,10))
ct<-nnct(ipd,cls)

Znnsym.ss(Y,cls)
Znnsym.ss.ct(ct)

Run the code above in your browser using DataLab