10_Functional_Programming

Question 1

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Answer 1

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Question 2

How do you iterate with purrr::map() variants?

Answer 2

map() returns list; map_dbl/map_int/map_chr enforce types.

Code:
library(purrr)
map_dbl(1:5, ~ .x^2)
map2_chr(letters[1:3], 1:3, ~ paste0(.x, .y))
pmap_dbl(list(a=1:3, b=4:6), ~ ..1 + ..2)

Question 3

How do you handle missing or failing iterations in purrr?

Answer 3

Use possibly() and safely() wrappers.

Code:
library(purrr)
safe_log <- safely(log, otherwise = NA_real_)
map_dbl(c(1, -1, 10), ~ safe_log(.x)$result)

Question 4

How do you reduce/accumulate values with purrr?

Answer 4

Use reduce() and accumulate().

Code:
library(purrr)
reduce(1:5, +) # 15
accumulate(1:5, +) # 1 3 6 10 15