StratifiedSampling (version 0.4.1)

stratifiedcube: Stratified Sampling

Description

This function implements a method for selecting a stratified sample. It really improves the performance of the function fbs and balstrat.

Usage

stratifiedcube(X, strata, pik, EPS = 1e-07)

Value

A vector with elements equal to 0 or 1. The value 1 indicates that the unit is selected while the value 0 is for rejected units.

Arguments

X

A matrix of size (\(N\) x \(p\)) of auxiliary variables on which the sample must be balanced.

strata

A vector of integers that specifies the stratification..

pik

A vector of inclusion probabilities.

EPS

epsilon value

Details

The function is selecting a balanced sample very quickly even if the sum of inclusion probabilities within strata are non-integer. The function should be used in preference. Firstly, a flight phase is performed on each strata. Secondly, the function findB is used to find a particular matrix to apply a flight phase by using the cube method proposed by Chauvet, G. and Tillé, Y. (2006). Finally, a landing phase is applied by suppression of variables.

References

Chauvet, G. and Tillé, Y. (2006). A fast algorithm of balanced sampling. Computational Statistics, 21/1:53-62

See Also

fbs, balstrat, landingRM, ffphase

Examples

N <- 100
n <- 10
p <- 4
X <- matrix(rgamma(N*p,4,25),ncol = p)
strata <- as.matrix(rep(1:n,each = N/n))
pik <- rep(n/N,N)

s <- stratifiedcube(X,strata,pik)

t(X/pik)%*%s
t(X/pik)%*%pik

Xcat <- disj(strata)

t(Xcat)%*%s
t(Xcat)%*%pik