sampling (version 2.9)

UPsampford: Sampford sampling

Description

Uses the Sampford's method to select a sample of units (unequal probabilities, without replacement, fixed sample size).

Usage

UPsampford(pik,eps=1e-6, max_iter=500)

Arguments

pik

vector of the inclusion probabilities.

eps

the control value, by default equal to 1e-6.

max_iter

maximum number of iterations in the algorithm.

Value

Returns a vector (with elements 0 and 1) of size N, the population size. Each element k of this vector indicates the status of unit k (1, unit k is selected in the sample; 0, otherwise). The value eps is used to control pik (pik>eps & pik < 1-eps). The sample size must be small with respect to the population size; otherwise, the selection time can be very long.

References

Sampford, M. (1967), On sampling without replacement with unequal probabilities of selection, Biometrika, 54:499-513.

See Also

UPsampfordpi2

Examples

# NOT RUN {
#define the prescribed inclusion probabilities
pik=c(0.2,0.7,0.8,0.5,0.4,0.4)
s=UPsampford(pik)
#the sample is
(1:length(pik))[s==1]
# }