View source: R/stratifiedcube.R
stratifiedcube | R Documentation |
This function implements a method for selecting a stratified sample. It really improves the performance of the function fbs
and balstrat
.
stratifiedcube(X, strata, pik, EPS = 1e-07)
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 |
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.
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.
Chauvet, G. and Tillé, Y. (2006). A fast algorithm of balanced sampling. Computational Statistics, 21/1:53-62
fbs
, balstrat
, landingRM
, ffphase
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
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