Each rectangle stands for a stratum, and the simple random sampling without replacement is performed within each stratum. The points being sampled are marked out (by red circles by default).
sample.strat(pop = ceiling(10 * runif(10, 0.5, 1)), size = ceiling(pop *
runif(length(pop), 0, 0.5)), p.col = c("blue", "red"), p.cex = c(1, 3),
...)a vector for the size of each stratum in the population.
a corresponding vector for the sample size in each stratum (recycled if necessary).
different colors /magnification rate to annotate the population and the sample
other arguments passed to rect to annotate the
``strata''
None (invisible `NULL').
Examples at https://yihui.name/animation/example/sample-strat/
sample, sample.simple,
sample.cluster, sample.ratio,
sample.system