StratifiedSampling (version 0.4.1)

ffphase: Fast flight phase of the cube method

Description

This function computes the flight phase of the cube method proposed by Chauvet and Tillé (2006).

Usage

ffphase(X, pik)

Value

Updated vector of pik that contains 0 and 1 for unit that are rejected or selected.

Arguments

X

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

pik

A vector of inclusion probabilities.

Author

Raphaël Jauslin

Details

This function implements the method proposed by (Chauvet and Tillé 2006). It recursively transforms the vector of inclusion probabilities pik into a sample that respects the balancing equations. The algorithm stops when the null space of the sub-matrix \(B\) is empty. For more information see (Chauvet and Tillé 2006).

The function uses the function Null to find the null space of the sub-matrix \(B\).

References

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

See Also

fastflightphase, flightphase.

Examples

N <- 100
n <- 10
p <- 4

pik <- rep(n/N,N)
X <- cbind(pik,matrix(rgamma(N*p,4,25),ncol= p))

pikstar <- ffphase(X,pik) 
t(X/pik)%*%pikstar
t(X/pik)%*%pik
pikstar