sample_random()
performs Simple Random Sampling or Stratified Random Samplingsample_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 between1-k
. The second element isr
+k
, and so on.
Usage
sample_random(data, n, prop, by = NULL, weight = NULL)
sample_systematic(data, n, r = NULL, by = NULL)
Arguments
- data
A data frame. If
data
is agrouped_df
, the operation will be performed on each group (stratified).- n, prop
Provide either
n
, the number of rows, orprop
, 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, usedplyr::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 between1:k
Examples
library(metan)
sample_random(data_ge, n = 5)
#> # A tibble: 5 × 5
#> ENV GEN REP GY HM
#> <fct> <fct> <fct> <dbl> <dbl>
#> 1 E14 G6 1 2.00 39
#> 2 E6 G9 2 2.85 47.5
#> 3 E1 G10 1 2.18 47.3
#> 4 E10 G8 2 2.89 45
#> 5 E14 G8 1 1.77 42
sample_random(data_ge,
n = 3,
by = ENV)
#> # A tibble: 42 × 5
#> ENV GEN REP GY HM
#> <fct> <fct> <fct> <dbl> <dbl>
#> 1 E1 G10 3 2.48 48.8
#> 2 E1 G1 1 2.17 44.9
#> 3 E1 G6 3 2.19 48.4
#> 4 E10 G7 3 2.18 43
#> 5 E10 G7 1 2.60 40
#> 6 E10 G6 2 2.53 47
#> 7 E11 G8 2 1.41 58
#> 8 E11 G9 1 1.01 53.7
#> 9 E11 G10 2 1.04 51
#> 10 E12 G4 3 1.44 53
#> # … with 32 more rows
sample_systematic(data_g, n = 6)
#> k = 6
#> # A tibble: 6 × 18
#> .id GEN REP PH EH EP EL ED CL CD CW KW NR
#> <dbl> <fct> <fct> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#> 1 2 H1 2 2.20 1.09 0.492 13.7 49.2 30.5 14.7 22.3 130. 16.4
#> 2 8 H11 2 2.09 1.06 0.509 12.2 46.9 26.5 14.3 13.5 114. 16.8
#> 3 14 H13 2 2.58 1.32 0.511 15.2 50.3 26.7 15.9 19.3 174. 20.4
#> 4 20 H3 2 1.96 0.926 0.473 15.5 46.2 27.4 16.2 17.8 135. 14
#> 5 26 H5 2 2.05 0.932 0.454 15.3 49.1 29.9 16.2 26.9 144. 18
#> 6 32 H7 2 2.14 1.05 0.489 13.8 46.2 27.8 14.3 23.0 135. 14.4
#> # … with 5 more variables: NKR <dbl>, CDED <dbl>, PERK <dbl>, TKW <dbl>,
#> # NKE <dbl>