sample_random() performs Simple Random Sampling or Stratified Random
Sampling
sample_systematic() performs systematic sampling. In this case, a regular
interval of size k (k = floor(N/n)) is generated considering the population
size (N) and desired sample size (n). Then, the starting member (r) is
randomly chosen between 1-k. The second element is r + k, and so on.
Usage
sample_random(data, n, prop, by = NULL, weight = NULL)
sample_systematic(data, n, r = NULL, by = NULL)
Value
An object of the same type as data.
Arguments
data
A data frame. If data is a grouped_df, the operation will be
performed on each group (stratified).
n, prop
Provide either n, the number of rows, or prop, the
proportion of rows to select. If neither are supplied, n = 1 will be
used.
by
A categorical variable to compute the sample by. It is a
shortcut to dplyr::group_by() that allows to group the data by one
categorical variable. If more than one grouping variable needs to be used,
use dplyr::group_by() to pass the data grouped.
weight
Sampling weights. This must evaluate to a vector of
non-negative numbers the same length as the input. Weights are
automatically standardised to sum to 1.
r
The starting element. By default, r is randomly selected between
1:k