Explain that bootstraps() is not upsampling or downsampling when using strata

demo_boot.md

library(rsample)
library(tidyverse)
library(palmerpenguins)
data("penguins")

penguins %>%
  count(species)
#> # A tibble: 3 x 2
#>   species       n
#>   <fct>     <int>
#> 1 Adelie      152
#> 2 Chinstrap    68
#> 3 Gentoo      124

penguin_folds <- bootstraps(penguins, strata = species)
penguin_folds
#> # Bootstrap sampling using stratification 
#> # A tibble: 25 x 2
#>    splits            id         
#>    <list>            <chr>      
#>  1 <split [344/130]> Bootstrap01
#>  2 <split [344/121]> Bootstrap02
#>  3 <split [344/121]> Bootstrap03
#>  4 <split [344/135]> Bootstrap04
#>  5 <split [344/125]> Bootstrap05
#>  6 <split [344/128]> Bootstrap06
#>  7 <split [344/120]> Bootstrap07
#>  8 <split [344/130]> Bootstrap08
#>  9 <split [344/132]> Bootstrap09
#> 10 <split [344/132]> Bootstrap10
#> # … with 15 more rows

penguin_folds %>%
  mutate(species_counts = map(splits, ~ analysis(.) %>% count(species))) %>%
  unnest(species_counts) %>%
  pivot_wider(names_from = species, values_from = n)
#> # A tibble: 25 x 5
#>    splits            id          Adelie Chinstrap Gentoo
#>    <list>            <chr>        <int>     <int>  <int>
#>  1 <split [344/130]> Bootstrap01    152        68    124
#>  2 <split [344/121]> Bootstrap02    152        68    124
#>  3 <split [344/121]> Bootstrap03    152        68    124
#>  4 <split [344/135]> Bootstrap04    152        68    124
#>  5 <split [344/125]> Bootstrap05    152        68    124
#>  6 <split [344/128]> Bootstrap06    152        68    124
#>  7 <split [344/120]> Bootstrap07    152        68    124
#>  8 <split [344/130]> Bootstrap08    152        68    124
#>  9 <split [344/132]> Bootstrap09    152        68    124
#> 10 <split [344/132]> Bootstrap10    152        68    124
#> # … with 15 more rows

^{Created on 2020-08-05 by the reprex package (v0.3.0.9001)}

Notice that the number of species in each bootstrap is the same because we used strata. No upsampling or downsampling happened.