tidyr - 获得组合的独特方式(仅使用 tidyverse) [英] tidyr - unique way to get combinations (using tidyverse only)

问题描述

我想使用 tidyverse(理想情况下)获取数据帧的唯一字符串列的所有唯一成对组合.

I wanted to get all unique pairwise combinations of a unique string column of a dataframe using the tidyverse (ideally).

这是一个虚拟示例:

library(tidyverse)

a <- letters[1:3] %>% 
        tibble::as_tibble()
a
#> # A tibble: 3 x 1
#>   value
#>   <chr>
#> 1     a
#> 2     b
#> 3     c

tidyr::crossing(a, a) %>% 
    magrittr::set_colnames(c("words1", "words2"))
#> # A tibble: 9 x 2
#>   words1 words2
#>    <chr>  <chr>
#> 1      a      a
#> 2      a      b
#> 3      a      c
#> 4      b      a
#> 5      b      b
#> 6      b      c
#> 7      c      a
#> 8      c      b
#> 9      c      c

有没有办法在这里删除重复"组合.在这个例子中，输出如下:

Is there a way to remove 'duplicate' combinations here. That is have the output be the following in this example:

# A tibble: 9 x 2
#>   words1 words2
#>    <chr>  <chr>
#> 1      a      b
#> 2      a      c
#> 3      b      c

我希望有一个很好的 purrr::map 或 filter 方法来完成上述操作.

I was hoping there would be a nice purrr::map or filter approach to pipe into to complete the above.

有与此类似的问题，例如此处，由@Sotos 标记.在这里，我专门寻找 tidyverse (purrr, dplyr) 方法来完成我设置的管道.其他答案使用了我不想作为依赖项包含在内的各种其他包.

There are similar questions to this one e.g. here, marked by @Sotos. Here I am specifically looking for tidyverse (purrr, dplyr) ways to complete the pipeline I have setup. The other answers use various other packages that I do not want to include as dependencies.

推荐答案

希望有更好的方法，但我通常使用这个...

wish there was a better way, but I usually use this...

library(tidyverse)

df <- tibble(value = letters[1:3])

df %>% 
  expand(value, value1 = value) %>% 
  filter(value < value1)

# # A tibble: 3 x 2
#   value value1
#   <chr> <chr> 
# 1 a     b     
# 2 a     c     
# 3 b     c  

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