tidyr 连接后，根据原始数据框对列进行排序

Question

在对两个数据框进行 tidyr 连接后，如何根据返回的原始数据框对返回的列进行排序？我在下面提出了几个解决方案。第一个感觉很笨拙。第二个可能不是好的做法。我想我错过了一些东西。

library(tidyverse)

a <- data_frame(x1 = LETTERS[1:3], x2 = 1:3)
b <- data_frame(x1 = LETTERS[c(1,2,4)], x3 = c(TRUE, FALSE, TRUE))

# Not the order I want
left_join(a, b, by = "x1")

# This is the order I want
a %>%
  left_join(b, by = "x1") %>%
  select(names(b), names(a)[!(names(a) %in% names(b))])

# This works too.
right_join(b, a, by = "x1") 

Answer 1

我想你可以做到unique(c(names(b), names(a))):

a %>%
    left_join(b, by = "x1") %>%
    select(unique(c(names(b), names(a))))

# A tibble: 3 x 3
#     x1    x3    x2
#  <chr> <lgl> <int>
#1     A  TRUE     1
#2     B FALSE     2
#3     C    NA     3