Cross-validation data frames

set.seed(42)

# Prepare the data frame containing the cross validation partitions
cv_split <- vfold_cv(___, v = ___)

cv_data <- cv_split %>% 
  mutate(
    # Extract the train data frame for each split
    train = map(___, ~___(.x)), 
    # Extract the validate data frame for each split
    validate = map(___, ~___(.x))
  )

# Use head() to preview cv_data
head(cv_data)