處理副詞結果

使用 purrr 的 R 語言中級函式程式設計

Colin Fay

Data Scientist & R Hacker at ThinkR

安全清理結果

用 transpose() 轉換結果：

# Transpose turn a list of n elements a and b 
# to a list of a and b, with each n elements
l <- list("a", 2, 3)
map(l, safe_log) %>% length()

map(l, safe_log) %>% transpose() %>% length()

compact() 會移除 NULL：

list(1, NULL, 3, 4, NULL) %>%
  compact()

[[1]]
[1] 1

[[2]]
[1] 3

[[3]]
[1] 4

otherwise = NULL %>% compact()：

l <- list(1,2,3,"a")
possible_log <- possibly(log, otherwise = NULL)
map(l, possible_log) %>% compact()

[[1]]
[1] 0

[[2]]
[1] 0.6931472

[[3]]
[1] 1.098612

使用 purrr 的 R 語言中級函式程式設計