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Iteratively draw a sequential Poisson sample

Source: R/sps_iterator.R
sps_iterator.Rd

Create a function that draws new units, one at a time, according to the sequential Poisson method without replacing previously sampled units.

Usage

sps_iterator(x, n = 0L, prn = NULL, alpha = 0.001, cutoff = Inf)

Arguments

x

[numeric >= 0] A positive and finite numeric vector of sizes for units in the population (e.g., revenue for drawing a sample of businesses).

n

[integer(1) >= 0] A positive integer giving the initial sample size for the iterator. The default is 0.

prn

[0 < numeric < 1] A numeric vector of permanent random numbers for units in the population, distributed uniform between 0 and 1. The default does not use permanent random numbers, instead generating a random vector when the function is called.

alpha

[0 <= numeric(1) <= 1] A number between 0 and 1. Units with inclusion probabilities greater than or equal to 1 - alpha are set to 1. The default is slightly larger than 0.

cutoff

[numeric(1) > 0] A numeric cutoff. Units with x >= cutoff get an inclusion probability of 1. The default does not apply a cutoff.

Value

A function that returns the next unit in the sample. It takes a single argument giving the sentinel value to indicate that there are no units left to sample (default NULL).

See also

sps() for drawing a sequential Poisson sample.

Examples

prn <- runif(5)
s <- sps_iterator(1:5, prn = prn)
s()
#> [1] 4
s()
#> [1] 3
s()
#> [1] 5

# Same as drawing the sample with 3 units.
sps(1:5, 3, prn = prn)
#> [1] 3 4 5