Question

我使用dplyr :: select来选择我的数据集的列。我观察了一个关于select_ with factor的有趣现象，并想知道为什么会这样。

我有一个4x3数据框，想要选择列“a”和“c”

x <- matrix(1:12, ncol = 3) %>% 
  as.data.frame() %>% 
  `colnames<-`(c("a","b", "c"))

# works, output: "a" "c"
x %>% select_(.dots = c("a", "c")) %>% colnames()

# change the search term to a factor, output wrong columns: "a" "b"
x %>% select_(.dots = as.factor(c("a", "c"))) %>% colnames()

你能不能暗示为什么会这样？

Answer 1

问题是factor在内部存储为整数。因此，它强制转换为整数，导致1,2和select选择前两个。通常，带有select_方法的.dots已过时。我们可以使用quosures或select_at，select_if等

x %>%
   select_at(vars(a, c))

或者

x %>% 
   select(a, c)

或者

x %>% 
  select(!!! quos(a, c))

dplyr :: select_ behavior with factor

1 个答案: