This package provides two functions for drawing stratified PRN-assisted samples: srs and pps. The former -- simple random sampling -- assumes that each unit \(k\) in a given stratum \(h\) is equally likely to be sampled, with inclusion probability $$\pi_k = \frac{n_h}{N_h}$$ for each stratum \(h\). The function then samples the \(n_h\) elements with the smallest PRN's, for each stratum \(h\).
The latter -- Pareto \(\pi ps\) sampling -- assumes that large units are more likely to be sampled than small units. The function approximates this unknown inclusion probability as $$\lambda_k = n_h \frac{x_k}{\sum_{i=1}^{n_h} x_i},$$ where \(x_k\) is a size measure, and samples the \(n_h\) elements with the smallest values of $$Q_k = \frac{PRN_k(1 - \lambda_k)}{\lambda_k(1 - PRN_k)},$$ for each stratum \(h\).
These two functions can be run standalone or via the wrapper function samp. Input to the functions is the sampling frame, stratification information and PRN's given as variables on the frame, and in the case for pps also a size measure given as variable on the frame. Output is a copy of the sampling frame containing sampling information, and in the case for pps also containing \(\lambda\) and \(Q\).
Provided is also a function transformprn via which it is possible to select where to start counting and in which direction when enumerating the PRN's in the sampling routines. This is done by specifying start and direction to transformprn and then calling srs or pps on its output.
Finally, an example dataset is provided that can be used to illustrate the functionality of the package.