2 purrr

2.1 Sample Using a Vector of Sizes

nested_iris <- 
  iris %>% 
  group_by(Species) %>% 
  nest() %>% 
  mutate(n = 2:4)
nested_iris %>% 
  mutate(subsamp = map2(data, n, sample_n)) %>% 
  select(Species, subsamp) %>% 
  unnest()

## # A tibble: 9 x 5
##   Species    Sepal.Length Sepal.Width Petal.Length Petal.Width
##   <fct>             <dbl>       <dbl>        <dbl>       <dbl>
## 1 setosa              5.4         3.9          1.7         0.4
## 2 setosa              5.1         3.4          1.5         0.2
## 3 versicolor          5.8         2.7          4.1         1  
## 4 versicolor          5.7         3            4.2         1.2
## 5 versicolor          5.9         3            4.2         1.5
## 6 virginica           6.3         2.7          4.9         1.8
## 7 virginica           7.2         3.6          6.1         2.5
## 8 virginica           6.1         3            4.9         1.8
## 9 virginica           5.6         2.8          4.9         2

Credit: @JennyBryan

2.2 Read in Multiple csv Files Into a Single data.frame

fs::dir_ls(data_dir, regexp = "\\.csv$") %>%
  map_dfr(read_csv)

Credit: @grrrck