r - 在 dplyr 链中使用 table()

Question

有人可以解释为什么table()在 dplyr-magrittr 管道操作链中不起作用？这是一个简单的reprex:

tibble(
  type = c("Fast", "Slow", "Fast", "Fast", "Slow"),
  colour = c("Blue", "Blue", "Red", "Red", "Red")
) %>% table(.$type, .$colour)

Error in sort.list(y) : 'x' must be atomic for 'sort.list' Have you called 'sort' on a list?

但这当然有效:

df <- tibble(
  type = c("Fast", "Slow", "Fast", "Fast", "Slow"),
  colour = c("Blue", "Blue", "Red", "Red", "Red")
) 

table(df$type, df$colour)


       Blue Red
  Fast    1   2
  Slow    1   1

Answer 1

此行为是设计使然:https://github.com/tidyverse/magrittr/blob/00a1fe3305a4914d7c9714fba78fd5f03f70f51e/README.md#re-using-the-placeholder-for-attributes

由于您没有 .就其本身而言，tibble 仍然作为第一个参数传递，所以它真的更像是

... %>% table(., .$type, .$colour)

官方的 magrittr 解决方法是使用花括号

... %>% {table(.$type, .$colour)}